diff --git a/src/Magnum/Array.h b/src/Magnum/Array.h
index efec033cb..bbf0abe05 100644
--- a/src/Magnum/Array.h
+++ b/src/Magnum/Array.h
@@ -204,7 +204,7 @@ template<class T> class Array3D: public Array<3, T> {
 };
 
 /** @debugoperator{Magnum::Array} */
-template<UnsignedInt dimensions, class T> Debug operator<<(Debug debug, const Array<dimensions, T>& value) {
+template<UnsignedInt dimensions, class T> Debug& operator<<(Debug& debug, const Array<dimensions, T>& value) {
     debug << "Array(";
     debug.setFlag(Debug::SpaceAfterEachValue, false);
     for(UnsignedInt i = 0; i != dimensions; ++i) {
@@ -217,17 +217,17 @@ template<UnsignedInt dimensions, class T> Debug operator<<(Debug debug, const Ar
 }
 
 /** @debugoperator{Magnum::Array1D} */
-template<class T> inline Debug operator<<(Debug debug, const Array1D<T>& value) {
+template<class T> inline Debug& operator<<(Debug& debug, const Array1D<T>& value) {
     return debug << static_cast<const Array<1, T>&>(value);
 }
 
 /** @debugoperator{Magnum::Array2D} */
-template<class T> inline Debug operator<<(Debug debug, const Array2D<T>& value) {
+template<class T> inline Debug& operator<<(Debug& debug, const Array2D<T>& value) {
     return debug << static_cast<const Array<2, T>&>(value);
 }
 
 /** @debugoperator{Magnum::Array3D} */
-template<class T> inline Debug operator<<(Debug debug, const Array3D<T>& value) {
+template<class T> inline Debug& operator<<(Debug& debug, const Array3D<T>& value) {
     return debug << static_cast<const Array<3, T>&>(value);
 }
 
diff --git a/src/Magnum/Attribute.cpp b/src/Magnum/Attribute.cpp
index 88a2feea1..5341634c3 100644
--- a/src/Magnum/Attribute.cpp
+++ b/src/Magnum/Attribute.cpp
@@ -139,7 +139,7 @@ UnsignedInt Attribute<Math::Vector<4, Float>>::size(GLint components, DataType d
     CORRADE_ASSERT_UNREACHABLE();
 }
 
-Debug operator<<(Debug debug, SizedAttribute<1, 1>::Components value) {
+Debug& operator<<(Debug& debug, SizedAttribute<1, 1>::Components value) {
     switch(value) {
         case SizedAttribute<1, 1>::Components::One:
             return debug << "Attribute::Components::One";
@@ -148,7 +148,7 @@ Debug operator<<(Debug debug, SizedAttribute<1, 1>::Components value) {
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, SizedAttribute<1, 2>::Components value) {
+Debug& operator<<(Debug& debug, SizedAttribute<1, 2>::Components value) {
     switch(value) {
         case SizedAttribute<1, 2>::Components::One:
             return debug << "Attribute::Components::One";
@@ -159,7 +159,7 @@ Debug operator<<(Debug debug, SizedAttribute<1, 2>::Components value) {
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, SizedAttribute<1, 3>::Components value) {
+Debug& operator<<(Debug& debug, SizedAttribute<1, 3>::Components value) {
     switch(value) {
         case SizedAttribute<1, 3>::Components::One:
             return debug << "Attribute::Components::One";
@@ -172,7 +172,7 @@ Debug operator<<(Debug debug, SizedAttribute<1, 3>::Components value) {
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, SizedAttribute<1, 4>::Components value) {
+Debug& operator<<(Debug& debug, SizedAttribute<1, 4>::Components value) {
     switch(value) {
         case SizedAttribute<1, 4>::Components::One:
             return debug << "Attribute::Components::One";
@@ -187,7 +187,7 @@ Debug operator<<(Debug debug, SizedAttribute<1, 4>::Components value) {
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, SizedMatrixAttribute<2>::Components value) {
+Debug& operator<<(Debug& debug, SizedMatrixAttribute<2>::Components value) {
     switch(value) {
         case SizedMatrixAttribute<2>::Components::Two:
             return debug << "Attribute::Components::Two";
@@ -196,7 +196,7 @@ Debug operator<<(Debug debug, SizedMatrixAttribute<2>::Components value) {
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, SizedMatrixAttribute<3>::Components value) {
+Debug& operator<<(Debug& debug, SizedMatrixAttribute<3>::Components value) {
     switch(value) {
         case SizedMatrixAttribute<3>::Components::Three:
             return debug << "Attribute::Components::Three";
@@ -205,7 +205,7 @@ Debug operator<<(Debug debug, SizedMatrixAttribute<3>::Components value) {
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, SizedMatrixAttribute<4>::Components value) {
+Debug& operator<<(Debug& debug, SizedMatrixAttribute<4>::Components value) {
     switch(value) {
         case SizedMatrixAttribute<4>::Components::Four:
             return debug << "Attribute::Components::Four";
@@ -214,7 +214,7 @@ Debug operator<<(Debug debug, SizedMatrixAttribute<4>::Components value) {
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, Attribute<Math::Vector<4, Float>>::Components value) {
+Debug& operator<<(Debug& debug, Attribute<Math::Vector<4, Float>>::Components value) {
     switch(value) {
         case Attribute<Math::Vector<4, Float>>::Components::One:
             return debug << "Attribute::Components::One";
@@ -233,7 +233,7 @@ Debug operator<<(Debug debug, Attribute<Math::Vector<4, Float>>::Components valu
     return debug << "Attribute::Components::(invalid)";
 }
 
-Debug operator<<(Debug debug, FloatAttribute::DataType value) {
+Debug& operator<<(Debug& debug, FloatAttribute::DataType value) {
     switch(value) {
         #define _c(value) case FloatAttribute::DataType::value: return debug << "Attribute::DataType::" #value;
         _c(UnsignedByte)
@@ -254,7 +254,7 @@ Debug operator<<(Debug debug, FloatAttribute::DataType value) {
 }
 
 #ifndef MAGNUM_TARGET_GLES2
-Debug operator<<(Debug debug, IntAttribute::DataType value) {
+Debug& operator<<(Debug& debug, IntAttribute::DataType value) {
     switch(value) {
         #define _c(value) case IntAttribute::DataType::value: return debug << "Attribute::DataType::" #value;
         _c(UnsignedByte)
@@ -271,7 +271,7 @@ Debug operator<<(Debug debug, IntAttribute::DataType value) {
 #endif
 
 #ifndef MAGNUM_TARGET_GLES
-Debug operator<<(Debug debug, DoubleAttribute::DataType value) {
+Debug& operator<<(Debug& debug, DoubleAttribute::DataType value) {
     switch(value) {
         #define _c(value) case DoubleAttribute::DataType::value: return debug << "Attribute::DataType::" #value;
         _c(Double)
@@ -282,7 +282,7 @@ Debug operator<<(Debug debug, DoubleAttribute::DataType value) {
 }
 #endif
 
-Debug operator<<(Debug debug, Attribute<Math::Vector<3, Float>>::DataType value) {
+Debug& operator<<(Debug& debug, Attribute<Math::Vector<3, Float>>::DataType value) {
     switch(value) {
         #define _c(value) case Attribute<Math::Vector<3, Float>>::DataType::value: return debug << "Attribute::DataType::" #value;
         _c(UnsignedByte)
@@ -303,7 +303,7 @@ Debug operator<<(Debug debug, Attribute<Math::Vector<3, Float>>::DataType value)
     return debug << "Attribute::DataType::(invalid)";
 }
 
-Debug operator<<(Debug debug, Attribute<Math::Vector<4, Float>>::DataType value) {
+Debug& operator<<(Debug& debug, Attribute<Math::Vector<4, Float>>::DataType value) {
     switch(value) {
         #define _c(value) case Attribute<Math::Vector<4, Float>>::DataType::value: return debug << "Attribute::DataType::" #value;
         _c(UnsignedByte)
diff --git a/src/Magnum/Attribute.h b/src/Magnum/Attribute.h
index 124926a79..950ba2d0d 100644
--- a/src/Magnum/Attribute.h
+++ b/src/Magnum/Attribute.h
@@ -297,10 +297,10 @@ template<UnsignedInt location, class T> class Attribute {
 
 #ifdef DOXYGEN_GENERATING_OUTPUT
 /** @debugoperatorclassenum{Magnum::Attribute,Magnum::Attribute::Components} */
-template<class T> Debug operator<<(Debug debug, Attribute<T>::Components);
+template<class T> Debug& operator<<(Debug& debug, Attribute<T>::Components);
 
 /** @debugoperatorclassenum{Magnum::Attribute,Magnum::Attribute::DataType} */
-template<class T> Debug operator<<(Debug debug, Attribute<T>::DataType);
+template<class T> Debug& operator<<(Debug& debug, Attribute<T>::DataType);
 #endif
 
 namespace Implementation {
@@ -328,10 +328,10 @@ template<> struct SizedAttribute<1, 4>: SizedVectorAttribute<1> {
     enum class Components: GLint { One = 1, Two = 2, Three = 3, Four = 4 };
     constexpr static Components DefaultComponents = Components::Four;
 };
-Debug MAGNUM_EXPORT operator<<(Debug debug, SizedAttribute<1, 1>::Components value);
-Debug MAGNUM_EXPORT operator<<(Debug debug, SizedAttribute<1, 2>::Components value);
-Debug MAGNUM_EXPORT operator<<(Debug debug, SizedAttribute<1, 3>::Components value);
-Debug MAGNUM_EXPORT operator<<(Debug debug, SizedAttribute<1, 4>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, SizedAttribute<1, 1>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, SizedAttribute<1, 2>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, SizedAttribute<1, 3>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, SizedAttribute<1, 4>::Components value);
 
 /* Matrix attribute sizes */
 template<std::size_t rows> struct SizedMatrixAttribute;
@@ -347,9 +347,9 @@ template<> struct SizedMatrixAttribute<4> {
     enum class Components: GLint { Four  = 4 };
     constexpr static Components DefaultComponents = Components::Four;
 };
-Debug MAGNUM_EXPORT operator<<(Debug debug, SizedMatrixAttribute<2>::Components value);
-Debug MAGNUM_EXPORT operator<<(Debug debug, SizedMatrixAttribute<3>::Components value);
-Debug MAGNUM_EXPORT operator<<(Debug debug, SizedMatrixAttribute<4>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, SizedMatrixAttribute<2>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, SizedMatrixAttribute<3>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, SizedMatrixAttribute<4>::Components value);
 template<> struct SizedAttribute<2, 2>: SizedVectorAttribute<2>, SizedMatrixAttribute<2> {};
 template<> struct SizedAttribute<3, 3>: SizedVectorAttribute<3>, SizedMatrixAttribute<3> {};
 template<> struct SizedAttribute<4, 4>: SizedVectorAttribute<4>, SizedMatrixAttribute<4> {};
@@ -400,7 +400,7 @@ struct FloatAttribute {
 
 CORRADE_ENUMSET_OPERATORS(FloatAttribute::DataOptions)
 
-Debug MAGNUM_EXPORT operator<<(Debug debug, FloatAttribute::DataType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, FloatAttribute::DataType value);
 
 #ifndef MAGNUM_TARGET_GLES2
 /* Base for int attributes */
@@ -425,7 +425,7 @@ struct IntAttribute {
 
 CORRADE_ENUMSET_OPERATORS(IntAttribute::DataOptions)
 
-Debug MAGNUM_EXPORT operator<<(Debug debug, IntAttribute::DataType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, IntAttribute::DataType value);
 
 /* Base for unsigned int attributes */
 struct UnsignedIntAttribute {
@@ -459,7 +459,7 @@ struct DoubleAttribute {
     static UnsignedInt MAGNUM_EXPORT size(GLint components, DataType dataType);
 };
 
-Debug MAGNUM_EXPORT operator<<(Debug debug, DoubleAttribute::DataType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DoubleAttribute::DataType value);
 #endif
 
 /* Floating-point three-component vector has additional data type compared to
@@ -495,7 +495,7 @@ template<> struct Attribute<Math::Vector<3, Float>>: SizedAttribute<1, 3> {
     static UnsignedInt MAGNUM_EXPORT size(GLint components, DataType dataType);
 };
 
-Debug MAGNUM_EXPORT operator<<(Debug debug, Attribute<Math::Vector<3, Float>>::DataType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Attribute<Math::Vector<3, Float>>::DataType value);
 
 /* Floating-point four-component vector is absolutely special case */
 template<> struct Attribute<Math::Vector<4, Float>> {
@@ -546,8 +546,8 @@ template<> struct Attribute<Math::Vector<4, Float>> {
     static UnsignedInt MAGNUM_EXPORT size(GLint components, DataType dataType);
 };
 
-Debug MAGNUM_EXPORT operator<<(Debug debug, Attribute<Math::Vector<4, Float>>::Components value);
-Debug MAGNUM_EXPORT operator<<(Debug debug, Attribute<Math::Vector<4, Float>>::DataType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Attribute<Math::Vector<4, Float>>::Components value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Attribute<Math::Vector<4, Float>>::DataType value);
 
 /* Common float, int, unsigned int and double scalar attributes */
 template<> struct Attribute<Float>: FloatAttribute, SizedAttribute<1, 1> {};
diff --git a/src/Magnum/Audio/Buffer.cpp b/src/Magnum/Audio/Buffer.cpp
index 433f44d59..270b3b61f 100644
--- a/src/Magnum/Audio/Buffer.cpp
+++ b/src/Magnum/Audio/Buffer.cpp
@@ -29,7 +29,7 @@
 
 namespace Magnum { namespace Audio {
 
-Debug operator<<(Debug debug, const Buffer::Format value) {
+Debug& operator<<(Debug& debug, const Buffer::Format value) {
     switch(value) {
         #define _c(value) case Buffer::Format::value: return debug << "Audio::Buffer::Format::" #value;
         _c(Mono8)
diff --git a/src/Magnum/Audio/Buffer.h b/src/Magnum/Audio/Buffer.h
index 5839407f1..1d3b0e60d 100644
--- a/src/Magnum/Audio/Buffer.h
+++ b/src/Magnum/Audio/Buffer.h
@@ -105,7 +105,7 @@ class Buffer {
 };
 
 /** @debugoperatorclassenum{Magnum::Audio::Buffer,Magnum::Audio::Buffer::Format} */
-Debug MAGNUM_AUDIO_EXPORT operator<<(Debug debug, Buffer::Format value);
+MAGNUM_AUDIO_EXPORT Debug& operator<<(Debug& debug, Buffer::Format value);
 
 inline Buffer::Buffer(Buffer&& other): _id(other._id) {
     other._id = 0;
diff --git a/src/Magnum/Audio/Renderer.cpp b/src/Magnum/Audio/Renderer.cpp
index 03b3a4b17..85214cf5d 100644
--- a/src/Magnum/Audio/Renderer.cpp
+++ b/src/Magnum/Audio/Renderer.cpp
@@ -29,7 +29,7 @@
 
 namespace Magnum { namespace Audio {
 
-Debug operator<<(Debug debug, const Renderer::Error value) {
+Debug& operator<<(Debug& debug, const Renderer::Error value) {
     switch(value) {
         #define _c(value) case Renderer::Error::value: return debug << "Audio::Renderer::Error::" #value;
         _c(NoError)
@@ -44,7 +44,7 @@ Debug operator<<(Debug debug, const Renderer::Error value) {
     return debug << "Audio::Renderer::Error::(invalid)";
 }
 
-Debug operator<<(Debug debug, const Renderer::DistanceModel value) {
+Debug& operator<<(Debug& debug, const Renderer::DistanceModel value) {
     switch(value) {
         #define _c(value) case Renderer::DistanceModel::value: return debug << "Audio::Renderer::DistanceModel::" #value;
         _c(None)
diff --git a/src/Magnum/Audio/Renderer.h b/src/Magnum/Audio/Renderer.h
index 523338762..bf158c717 100644
--- a/src/Magnum/Audio/Renderer.h
+++ b/src/Magnum/Audio/Renderer.h
@@ -260,10 +260,10 @@ class Renderer {
 };
 
 /** @debugoperatorclassenum{Magnum::Audio::Renderer,Magnum::Audio::Renderer::Error} */
-Debug MAGNUM_AUDIO_EXPORT operator<<(Debug debug, Renderer::Error value);
+MAGNUM_AUDIO_EXPORT Debug& operator<<(Debug& debug, Renderer::Error value);
 
 /** @debugoperatorclassenum{Magnum::Audio::Renderer,Magnum::Audio::Renderer::DistanceModel} */
-Debug MAGNUM_AUDIO_EXPORT operator<<(Debug debug, Renderer::DistanceModel value);
+MAGNUM_AUDIO_EXPORT Debug& operator<<(Debug& debug, Renderer::DistanceModel value);
 
 }}
 
diff --git a/src/Magnum/Audio/Source.cpp b/src/Magnum/Audio/Source.cpp
index 4daf5b3ca..cdc9463cb 100644
--- a/src/Magnum/Audio/Source.cpp
+++ b/src/Magnum/Audio/Source.cpp
@@ -96,7 +96,7 @@ void Source::rewind(const std::vector<std::reference_wrapper<Source>>& sources)
     alSourceRewindv(ids.size(), ids);
 }
 
-Debug operator<<(Debug debug, const Source::State value) {
+Debug& operator<<(Debug& debug, const Source::State value) {
     switch(value) {
         #define _c(value) case Source::State::value: return debug << "Audio::Source::State::" #value;
         _c(Initial)
diff --git a/src/Magnum/Audio/Source.h b/src/Magnum/Audio/Source.h
index 2eb0dcce9..103fdcf09 100644
--- a/src/Magnum/Audio/Source.h
+++ b/src/Magnum/Audio/Source.h
@@ -701,7 +701,7 @@ class MAGNUM_AUDIO_EXPORT Source {
 };
 
 /** @debugoperatorclassenum{Magnum::Audio::Source,Magnum::Audio::Source::State} */
-Debug MAGNUM_AUDIO_EXPORT operator<<(Debug debug, Source::State value);
+MAGNUM_AUDIO_EXPORT Debug& operator<<(Debug& debug, Source::State value);
 
 inline Source::Source(Source&& other): _id(other._id) {
     other._id = 0;
diff --git a/src/Magnum/Buffer.cpp b/src/Magnum/Buffer.cpp
index 86c29197d..7b11a5534 100644
--- a/src/Magnum/Buffer.cpp
+++ b/src/Magnum/Buffer.cpp
@@ -622,7 +622,7 @@ bool Buffer::unmapImplementationDSAEXT() {
 #endif
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, Buffer::TargetHint value) {
+Debug& operator<<(Debug& debug, Buffer::TargetHint value) {
     switch(value) {
         #define _c(value) case Buffer::TargetHint::value: return debug << "Buffer::TargetHint::" #value;
         _c(Array)
@@ -661,7 +661,7 @@ Debug operator<<(Debug debug, Buffer::TargetHint value) {
 
 #if !defined(MAGNUM_TARGET_GLES2) || defined(MAGNUM_BUILD_DEPRECATED)
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, Buffer::Target value) {
+Debug& operator<<(Debug& debug, Buffer::Target value) {
     switch(value) {
         #ifndef MAGNUM_TARGET_GLES2
         #define _c(value) case Buffer::Target::value: return debug << "Buffer::Target::" #value;
diff --git a/src/Magnum/Buffer.h b/src/Magnum/Buffer.h
index 535a245db..f53ea141e 100644
--- a/src/Magnum/Buffer.h
+++ b/src/Magnum/Buffer.h
@@ -1431,11 +1431,11 @@ CORRADE_ENUMSET_OPERATORS(Buffer::MapFlags)
 #endif
 
 /** @debugoperatorclassenum{Magnum::Buffer,Magnum::Buffer::TargetHint} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Buffer::TargetHint value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Buffer::TargetHint value);
 
 #if !defined(MAGNUM_TARGET_GLES2) || defined(MAGNUM_BUILD_DEPRECATED)
 /** @debugoperatorclassenum{Magnum::Buffer,Magnum::Buffer::Target} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Buffer::Target value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Buffer::Target value);
 #endif
 
 inline Buffer::Buffer(NoCreateT) noexcept: _id{0}, _targetHint{TargetHint::Array}, _flags{ObjectFlag::DeleteOnDestruction}
diff --git a/src/Magnum/Context.cpp b/src/Magnum/Context.cpp
index 450836704..a82b8ae7c 100644
--- a/src/Magnum/Context.cpp
+++ b/src/Magnum/Context.cpp
@@ -700,7 +700,7 @@ void Context::resetState(const States states) {
 
 #ifndef MAGNUM_TARGET_WEBGL
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const Context::Flag value) {
+Debug& operator<<(Debug& debug, const Context::Flag value) {
     switch(value) {
         #define _c(value) case Context::Flag::value: return debug << "Context::Flag::" #value;
         _c(Debug)
diff --git a/src/Magnum/Context.h b/src/Magnum/Context.h
index 1ac5214a6..239d34f9e 100644
--- a/src/Magnum/Context.h
+++ b/src/Magnum/Context.h
@@ -485,7 +485,7 @@ class MAGNUM_EXPORT Context {
 
 #ifndef MAGNUM_TARGET_WEBGL
 /** @debugoperatorclassenum{Magnum::Context,Magnum::Context::Flag} */
-MAGNUM_EXPORT Debug operator<<(Debug debug, Context::Flag value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Context::Flag value);
 #endif
 
 /** @hideinitializer
diff --git a/src/Magnum/DebugOutput.cpp b/src/Magnum/DebugOutput.cpp
index 4d8b60860..966d8f6cc 100644
--- a/src/Magnum/DebugOutput.cpp
+++ b/src/Magnum/DebugOutput.cpp
@@ -225,7 +225,7 @@ void DebugOutput::callbackImplementationKhr(const Callback callback, const void*
 }
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const DebugOutput::Source value) {
+Debug& operator<<(Debug& debug, const DebugOutput::Source value) {
     switch(value) {
         #define _c(value) case DebugOutput::Source::value: return debug << "DebugOutput::Source::" #value;
         _c(Api)
@@ -240,7 +240,7 @@ Debug operator<<(Debug debug, const DebugOutput::Source value) {
     return debug << "DebugOutput::Source::(invalid)";
 }
 
-Debug operator<<(Debug debug, const DebugOutput::Type value) {
+Debug& operator<<(Debug& debug, const DebugOutput::Type value) {
     switch(value) {
         #define _c(value) case DebugOutput::Type::value: return debug << "DebugOutput::Type::" #value;
         _c(Error)
@@ -258,7 +258,7 @@ Debug operator<<(Debug debug, const DebugOutput::Type value) {
     return debug << "DebugOutput::Type::(invalid)";
 }
 
-Debug operator<<(Debug debug, const DebugOutput::Severity value) {
+Debug& operator<<(Debug& debug, const DebugOutput::Severity value) {
     switch(value) {
         #define _c(value) case DebugOutput::Severity::value: return debug << "DebugOutput::Severity::" #value;
         _c(High)
@@ -312,7 +312,7 @@ void DebugMessage::insertImplementationGremedy(Source, Type, UnsignedInt, DebugO
 #endif
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const DebugMessage::Source value) {
+Debug& operator<<(Debug& debug, const DebugMessage::Source value) {
     switch(value) {
         #define _c(value) case DebugMessage::Source::value: return debug << "DebugMessage::Source::" #value;
         _c(ThirdParty)
@@ -330,7 +330,7 @@ Debug operator<<(Debug debug, const DebugMessage::Source value) {
     return debug << "DebugMessage::Source::(invalid)";
 }
 
-Debug operator<<(Debug debug, const DebugMessage::Type value) {
+Debug& operator<<(Debug& debug, const DebugMessage::Type value) {
     switch(value) {
         #define _c(value) case DebugMessage::Type::value: return debug << "DebugMessage::Type::" #value;
         _c(Error)
@@ -424,7 +424,7 @@ void DebugGroup::popImplementationExt() {
 }
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const DebugGroup::Source value) {
+Debug& operator<<(Debug& debug, const DebugGroup::Source value) {
     switch(value) {
         #define _c(value) case DebugGroup::Source::value: return debug << "DebugGroup::Source::" #value;
         _c(ThirdParty)
diff --git a/src/Magnum/DebugOutput.h b/src/Magnum/DebugOutput.h
index 344b412ba..ba06e79c0 100644
--- a/src/Magnum/DebugOutput.h
+++ b/src/Magnum/DebugOutput.h
@@ -418,13 +418,13 @@ class MAGNUM_EXPORT DebugOutput {
 };
 
 /** @debugoperatorclassenum{Magnum::DebugOutput,Magnum::DebugOutput::Source} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, DebugOutput::Source value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DebugOutput::Source value);
 
 /** @debugoperatorclassenum{Magnum::DebugOutput,Magnum::DebugOutput::Type} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, DebugOutput::Type value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DebugOutput::Type value);
 
 /** @debugoperatorclassenum{Magnum::DebugOutput,Magnum::DebugOutput::Severity} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, DebugOutput::Severity value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DebugOutput::Severity value);
 
 /**
 @brief Debug message
@@ -691,10 +691,10 @@ class MAGNUM_EXPORT DebugMessage {
 };
 
 /** @debugoperatorclassenum{Magnum::DebugMessage,Magnum::DebugMessage::Source} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, DebugMessage::Source value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DebugMessage::Source value);
 
 /** @debugoperatorclassenum{Magnum::DebugMessage,Magnum::DebugMessage::Type} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, DebugMessage::Type value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DebugMessage::Type value);
 
 /**
 @brief Debug group
@@ -904,7 +904,7 @@ class MAGNUM_EXPORT DebugGroup {
 };
 
 /** @debugoperatorclassenum{Magnum::DebugGroup,Magnum::DebugGroup::Source} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, DebugGroup::Source value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DebugGroup::Source value);
 
 }
 #else
diff --git a/src/Magnum/DefaultFramebuffer.cpp b/src/Magnum/DefaultFramebuffer.cpp
index 58d2dfc42..0f4b8949e 100644
--- a/src/Magnum/DefaultFramebuffer.cpp
+++ b/src/Magnum/DefaultFramebuffer.cpp
@@ -115,7 +115,7 @@ void DefaultFramebuffer::initializeContextBasedFunctionality(Context& context) {
 }
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const DefaultFramebuffer::Status value) {
+Debug& operator<<(Debug& debug, const DefaultFramebuffer::Status value) {
     switch(value) {
         #define _c(value) case DefaultFramebuffer::Status::value: return debug << "DefaultFramebuffer::Status::" #value;
         _c(Complete)
diff --git a/src/Magnum/DefaultFramebuffer.h b/src/Magnum/DefaultFramebuffer.h
index 104567fae..5467145f9 100644
--- a/src/Magnum/DefaultFramebuffer.h
+++ b/src/Magnum/DefaultFramebuffer.h
@@ -476,7 +476,7 @@ class MAGNUM_EXPORT DefaultFramebuffer: public AbstractFramebuffer {
 extern DefaultFramebuffer MAGNUM_EXPORT defaultFramebuffer;
 
 /** @debugoperatorclassenum{Magnum::DefaultFramebuffer,Magnum::DefaultFramebuffer::Status} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, DefaultFramebuffer::Status value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, DefaultFramebuffer::Status value);
 
 }
 
diff --git a/src/Magnum/Framebuffer.cpp b/src/Magnum/Framebuffer.cpp
index 44a5e6e26..d39e1f6a1 100644
--- a/src/Magnum/Framebuffer.cpp
+++ b/src/Magnum/Framebuffer.cpp
@@ -349,7 +349,7 @@ void Framebuffer::textureLayerImplementationDSAEXT(BufferAttachment attachment,
 #endif
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const Framebuffer::Status value) {
+Debug& operator<<(Debug& debug, const Framebuffer::Status value) {
     switch(value) {
         #define _c(value) case Framebuffer::Status::value: return debug << "Framebuffer::Status::" #value;
         _c(Complete)
diff --git a/src/Magnum/Framebuffer.h b/src/Magnum/Framebuffer.h
index 55862c01d..5c3706da7 100644
--- a/src/Magnum/Framebuffer.h
+++ b/src/Magnum/Framebuffer.h
@@ -785,7 +785,7 @@ class MAGNUM_EXPORT Framebuffer: public AbstractFramebuffer, public AbstractObje
 };
 
 /** @debugoperatorclassenum{Magnum::Framebuffer,Magnum::Framebuffer::Status} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Framebuffer::Status value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Framebuffer::Status value);
 
 inline Framebuffer::Framebuffer(Framebuffer&& other) noexcept {
     _id = other._id;
diff --git a/src/Magnum/Math/Angle.h b/src/Magnum/Math/Angle.h
index 411f08a47..6bd1cd45b 100644
--- a/src/Magnum/Math/Angle.h
+++ b/src/Magnum/Math/Angle.h
@@ -237,7 +237,7 @@ template<class T> constexpr Deg<T>::Deg(Unit<Rad, T> value): Unit<Math::Deg, T>(
 template<class T> constexpr Rad<T>::Rad(Unit<Deg, T> value): Unit<Math::Rad, T>(T(value)*Math::Constants<T>::pi()/T(180)) {}
 
 /** @debugoperator{Magnum::Math::Rad} */
-template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Unit<Rad, T>& value) {
+template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Unit<Rad, T>& value) {
     debug << "Rad(";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << T(value) << ")";
@@ -246,7 +246,7 @@ template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug deb
 }
 
 /** @debugoperator{Magnum::Math::Deg} */
-template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Unit<Deg, T>& value) {
+template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Unit<Deg, T>& value) {
     debug << "Deg(";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << T(value) << ")";
@@ -256,11 +256,11 @@ template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug deb
 
 /* Explicit instantiation for commonly used types */
 #ifndef DOXYGEN_GENERATING_OUTPUT
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Unit<Rad, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Unit<Deg, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Rad, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Deg, Float>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Unit<Rad, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Unit<Deg, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Rad, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Deg, Double>&);
 #endif
 #endif
 
diff --git a/src/Magnum/Math/BoolVector.h b/src/Magnum/Math/BoolVector.h
index e3f0e4b77..3acd12e20 100644
--- a/src/Magnum/Math/BoolVector.h
+++ b/src/Magnum/Math/BoolVector.h
@@ -223,7 +223,7 @@ template<std::size_t size> class BoolVector {
 };
 
 /** @debugoperator{Magnum::Math::BoolVector} */
-template<std::size_t size> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const BoolVector<size>& value) {
+template<std::size_t size> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const BoolVector<size>& value) {
     debug << "BoolVector(";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     for(std::size_t i = 0; i != size; ++i) {
diff --git a/src/Magnum/Math/Color.h b/src/Magnum/Math/Color.h
index 949438720..e36c54422 100644
--- a/src/Magnum/Math/Color.h
+++ b/src/Magnum/Math/Color.h
@@ -534,12 +534,12 @@ MAGNUM_VECTORn_OPERATOR_IMPLEMENTATION(4, Color4)
 #endif
 
 /** @debugoperator{Magnum::Math::Color3} */
-template<class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Color3<T>& value) {
+template<class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Color3<T>& value) {
     return debug << static_cast<const Vector3<T>&>(value);
 }
 
 /** @debugoperator{Magnum::Math::Color4} */
-template<class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Color4<T>& value) {
+template<class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Color4<T>& value) {
     return debug << static_cast<const Vector4<T>&>(value);
 }
 
diff --git a/src/Magnum/Math/Complex.h b/src/Magnum/Math/Complex.h
index ce898204e..fac9476d1 100644
--- a/src/Magnum/Math/Complex.h
+++ b/src/Magnum/Math/Complex.h
@@ -476,7 +476,7 @@ template<class T> inline Complex<T> operator/(T scalar, const Complex<T>& comple
 }
 
 /** @debugoperator{Magnum::Math::Complex} */
-template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Complex<T>& value) {
+template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Complex<T>& value) {
     debug << "Complex(";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << value.real() << ", " << value.imaginary() << ")";
@@ -486,9 +486,9 @@ template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug deb
 
 /* Explicit instantiation for commonly used types */
 #ifndef DOXYGEN_GENERATING_OUTPUT
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Complex<Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Complex<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Complex<Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Complex<Double>&);
 #endif
 #endif
 
diff --git a/src/Magnum/Math/Dual.h b/src/Magnum/Math/Dual.h
index 83f2df9fe..038f2e7df 100644
--- a/src/Magnum/Math/Dual.h
+++ b/src/Magnum/Math/Dual.h
@@ -209,7 +209,7 @@ template<class T> class Dual {
 #endif
 
 /** @debugoperator{Magnum::Math::Dual} */
-template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Dual<T>& value) {
+template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Dual<T>& value) {
     debug << "Dual(";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << value.real() << ", " << value.dual() << ")";
diff --git a/src/Magnum/Math/DualComplex.h b/src/Magnum/Math/DualComplex.h
index 7e4084016..f3082c0c4 100644
--- a/src/Magnum/Math/DualComplex.h
+++ b/src/Magnum/Math/DualComplex.h
@@ -369,7 +369,7 @@ template<class T> class DualComplex: public Dual<Complex<T>> {
 };
 
 /** @debugoperator{Magnum::Math::DualQuaternion} */
-template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const DualComplex<T>& value) {
+template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const DualComplex<T>& value) {
     debug << "DualComplex({";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << value.real().real() << ", " << value.real().imaginary() << "}, {"
@@ -380,9 +380,9 @@ template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug deb
 
 /* Explicit instantiation for commonly used types */
 #ifndef DOXYGEN_GENERATING_OUTPUT
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const DualComplex<Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualComplex<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const DualComplex<Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualComplex<Double>&);
 #endif
 #endif
 
diff --git a/src/Magnum/Math/DualQuaternion.h b/src/Magnum/Math/DualQuaternion.h
index 11c0e5953..9c7af521c 100644
--- a/src/Magnum/Math/DualQuaternion.h
+++ b/src/Magnum/Math/DualQuaternion.h
@@ -358,7 +358,7 @@ template<class T> class DualQuaternion: public Dual<Quaternion<T>> {
 };
 
 /** @debugoperator{Magnum::Math::DualQuaternion} */
-template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const DualQuaternion<T>& value) {
+template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const DualQuaternion<T>& value) {
     debug << "DualQuaternion({{";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << value.real().vector().x() << ", " << value.real().vector().y() << ", " << value.real().vector().z()
@@ -371,9 +371,9 @@ template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug deb
 
 /* Explicit instantiation for commonly used types */
 #ifndef DOXYGEN_GENERATING_OUTPUT
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const DualQuaternion<Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualQuaternion<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const DualQuaternion<Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualQuaternion<Double>&);
 #endif
 #endif
 
diff --git a/src/Magnum/Math/Matrix.h b/src/Magnum/Math/Matrix.h
index 161ad0100..de7012484 100644
--- a/src/Magnum/Math/Matrix.h
+++ b/src/Magnum/Math/Matrix.h
@@ -266,7 +266,7 @@ template<class T> using Matrix4x4 = Matrix<4, T>;
 MAGNUM_MATRIX_OPERATOR_IMPLEMENTATION(Matrix<size, T>)
 
 /** @debugoperator{Magnum::Math::Matrix} */
-template<std::size_t size, class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Matrix<size, T>& value) {
+template<std::size_t size, class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Matrix<size, T>& value) {
     return debug << static_cast<const RectangularMatrix<size, size, T>&>(value);
 }
 
diff --git a/src/Magnum/Math/Matrix3.h b/src/Magnum/Math/Matrix3.h
index 1defefd43..f4702db42 100644
--- a/src/Magnum/Math/Matrix3.h
+++ b/src/Magnum/Math/Matrix3.h
@@ -380,7 +380,7 @@ MAGNUM_MATRIXn_OPERATOR_IMPLEMENTATION(3, Matrix3)
 #endif
 
 /** @debugoperator{Magnum::Math::Matrix3} */
-template<class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Matrix3<T>& value) {
+template<class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Matrix3<T>& value) {
     return debug << static_cast<const Matrix3x3<T>&>(value);
 }
 
diff --git a/src/Magnum/Math/Matrix4.h b/src/Magnum/Math/Matrix4.h
index b224beaa1..1a209460a 100644
--- a/src/Magnum/Math/Matrix4.h
+++ b/src/Magnum/Math/Matrix4.h
@@ -481,7 +481,7 @@ MAGNUM_MATRIXn_OPERATOR_IMPLEMENTATION(4, Matrix4)
 #endif
 
 /** @debugoperator{Magnum::Math::Matrix4} */
-template<class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Matrix4<T>& value) {
+template<class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Matrix4<T>& value) {
     return debug << static_cast<const Matrix4x4<T>&>(value);
 }
 
diff --git a/src/Magnum/Math/Quaternion.h b/src/Magnum/Math/Quaternion.h
index d09eab8c6..ca633ab78 100644
--- a/src/Magnum/Math/Quaternion.h
+++ b/src/Magnum/Math/Quaternion.h
@@ -532,7 +532,7 @@ template<class T> inline Quaternion<T> operator/(T scalar, const Quaternion<T>&
 }
 
 /** @debugoperator{Magnum::Math::Quaternion} */
-template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Quaternion<T>& value) {
+template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Quaternion<T>& value) {
     debug << "Quaternion({";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << value.vector().x() << ", " << value.vector().y() << ", " << value.vector().z() << "}, " << value.scalar() << ")";
@@ -542,9 +542,9 @@ template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug deb
 
 /* Explicit instantiation for commonly used types */
 #ifndef DOXYGEN_GENERATING_OUTPUT
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Quaternion<Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Quaternion<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Quaternion<Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Quaternion<Double>&);
 #endif
 #endif
 
diff --git a/src/Magnum/Math/Range.h b/src/Magnum/Math/Range.h
index 771b4202b..baee7986a 100644
--- a/src/Magnum/Math/Range.h
+++ b/src/Magnum/Math/Range.h
@@ -529,7 +529,7 @@ template<class T> class Range3D: public Range<3, T> {
 };
 
 /** @debugoperator{Magnum::Math::Range} */
-template<UnsignedInt dimensions, class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Range<dimensions, T>& value) {
+template<UnsignedInt dimensions, class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Range<dimensions, T>& value) {
     debug << "Range({";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << value.min()[0];
diff --git a/src/Magnum/Math/RectangularMatrix.h b/src/Magnum/Math/RectangularMatrix.h
index c8e43983d..b7b333c97 100644
--- a/src/Magnum/Math/RectangularMatrix.h
+++ b/src/Magnum/Math/RectangularMatrix.h
@@ -526,7 +526,7 @@ template<std::size_t size, std::size_t cols, class T> inline RectangularMatrix<c
 }
 
 /** @debugoperator{Magnum::Math::RectangularMatrix} */
-template<std::size_t cols, std::size_t rows, class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::RectangularMatrix<cols, rows, T>& value) {
+template<std::size_t cols, std::size_t rows, class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Magnum::Math::RectangularMatrix<cols, rows, T>& value) {
     debug << "Matrix(";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     for(std::size_t row = 0; row != rows; ++row) {
@@ -544,29 +544,29 @@ template<std::size_t cols, std::size_t rows, class T> Corrade::Utility::Debug op
 #ifndef DOXYGEN_GENERATING_OUTPUT
 /* Explicit instantiation for types used in OpenGL */
 /* Square matrices */
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 2, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 3, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 4, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 2, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 3, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 4, Float>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 2, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 3, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 4, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 2, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 3, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 4, Double>&);
 #endif
 
 /* Rectangular matrices */
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 3, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 2, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 4, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 2, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 4, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 3, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 3, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 2, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 4, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 2, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 4, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 3, Float>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 3, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 2, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 4, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 2, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 4, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 3, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 3, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 2, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 4, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 2, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 4, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 3, Double>&);
 #endif
 
 #define MAGNUM_RECTANGULARMATRIX_SUBCLASS_IMPLEMENTATION(cols, rows, ...)   \
diff --git a/src/Magnum/Math/Test/UnitTest.cpp b/src/Magnum/Math/Test/UnitTest.cpp
index d677681e4..45618351b 100644
--- a/src/Magnum/Math/Test/UnitTest.cpp
+++ b/src/Magnum/Math/Test/UnitTest.cpp
@@ -63,7 +63,7 @@ typedef Unit<Sec_, Float> Sec;
 typedef Unit<Sec_, Int> Seci;
 typedef Constants<Float> Constants;
 
-inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, Sec value) {
+inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, Sec value) {
     return debug << Float(value);
 }
 
diff --git a/src/Magnum/Math/Vector.h b/src/Magnum/Math/Vector.h
index 29023512d..25fcc0836 100644
--- a/src/Magnum/Math/Vector.h
+++ b/src/Magnum/Math/Vector.h
@@ -1069,7 +1069,7 @@ operator/(const Vector<size, Integral>& a, const Vector<size, FloatingPoint>& b)
 }
 
 /** @debugoperator{Magnum::Math::Vector} */
-template<std::size_t size, class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Vector<size, T>& value) {
+template<std::size_t size, class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Vector<size, T>& value) {
     debug << "Vector(";
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     for(std::size_t i = 0; i != size; ++i) {
@@ -1083,19 +1083,19 @@ template<std::size_t size, class T> Corrade::Utility::Debug operator<<(Corrade::
 
 /* Explicit instantiation for types used in OpenGL */
 #ifndef DOXYGEN_GENERATING_OUTPUT
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<2, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<3, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<4, Float>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<2, Int>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<3, Int>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<4, Int>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<2, UnsignedInt>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<3, UnsignedInt>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<4, UnsignedInt>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, Int>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, Int>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, Int>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, UnsignedInt>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, UnsignedInt>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, UnsignedInt>&);
 #ifndef MAGNUM_TARGET_GLES
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<2, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<3, Double>&);
-extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utility::Debug, const Vector<4, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, Double>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, Double>&);
 #endif
 #endif
 
diff --git a/src/Magnum/Math/Vector2.h b/src/Magnum/Math/Vector2.h
index 8d4088e0e..5aca64b59 100644
--- a/src/Magnum/Math/Vector2.h
+++ b/src/Magnum/Math/Vector2.h
@@ -214,7 +214,7 @@ MAGNUM_VECTORn_OPERATOR_IMPLEMENTATION(2, Vector2)
 #endif
 
 /** @debugoperator{Magnum::Math::Vector2} */
-template<class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Vector2<T>& value) {
+template<class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Vector2<T>& value) {
     return debug << static_cast<const Vector<2, T>&>(value);
 }
 
diff --git a/src/Magnum/Math/Vector3.h b/src/Magnum/Math/Vector3.h
index 26774fc2b..83b0fdc89 100644
--- a/src/Magnum/Math/Vector3.h
+++ b/src/Magnum/Math/Vector3.h
@@ -267,7 +267,7 @@ MAGNUM_VECTORn_OPERATOR_IMPLEMENTATION(3, Vector3)
 #endif
 
 /** @debugoperator{Magnum::Math::Vector3} */
-template<class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Vector3<T>& value) {
+template<class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Vector3<T>& value) {
     return debug << static_cast<const Vector<3, T>&>(value);
 }
 
diff --git a/src/Magnum/Math/Vector4.h b/src/Magnum/Math/Vector4.h
index 6d465df68..ad1490b6a 100644
--- a/src/Magnum/Math/Vector4.h
+++ b/src/Magnum/Math/Vector4.h
@@ -221,7 +221,7 @@ MAGNUM_VECTORn_OPERATOR_IMPLEMENTATION(4, Vector4)
 #endif
 
 /** @debugoperator{Magnum::Math::Vector4} */
-template<class T> inline Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Vector4<T>& value) {
+template<class T> inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Vector4<T>& value) {
     return debug << static_cast<const Vector<4, T>&>(value);
 }
 
diff --git a/src/Magnum/Math/instantiation.cpp b/src/Magnum/Math/instantiation.cpp
index e0d70be44..0ad1bfa12 100644
--- a/src/Magnum/Math/instantiation.cpp
+++ b/src/Magnum/Math/instantiation.cpp
@@ -84,24 +84,24 @@ template struct ConfigurationValue<Magnum::Math::Range<3, Magnum::Double>>;
 namespace Magnum { namespace Math {
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Complex<Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Complex<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Complex<Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Complex<Double>&);
 #endif
 
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const DualComplex<Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualComplex<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const DualComplex<Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualComplex<Double>&);
 #endif
 
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const DualQuaternion<Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualQuaternion<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const DualQuaternion<Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const DualQuaternion<Double>&);
 #endif
 
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Quaternion<Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Quaternion<Float>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Quaternion<Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Quaternion<Double>&);
 #endif
 
 /* Check proper size of GL types */
@@ -144,50 +144,50 @@ static_assert(sizeof(RectangularMatrix<3, 4, Double>) == 96, "Improper size of 3
 static_assert(sizeof(RectangularMatrix<4, 3, Double>) == 96, "Improper size of 4x3 Double matrix");
 #endif
 
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 2, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 3, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 4, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 2, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 3, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 4, Float>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 2, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 3, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 4, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 2, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 3, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 4, Double>&);
 #endif
 
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 3, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 2, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 4, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 2, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 4, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 3, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 3, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 2, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 4, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 2, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 4, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 3, Float>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 3, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 2, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<2, 4, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 2, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<3, 4, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const RectangularMatrix<4, 3, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 3, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 2, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<2, 4, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 2, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<3, 4, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const RectangularMatrix<4, 3, Double>&);
 #endif
 
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Unit<Rad, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Unit<Deg, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Rad, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Deg, Float>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Unit<Rad, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Unit<Deg, Double>&);
-#endif
-
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<2, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<3, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<4, Float>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<2, Int>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<3, Int>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<4, Int>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<2, UnsignedInt>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<3, UnsignedInt>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<4, UnsignedInt>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Rad, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Deg, Double>&);
+#endif
+
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, Float>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, Int>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, Int>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, Int>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, UnsignedInt>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, UnsignedInt>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, UnsignedInt>&);
 #ifndef MAGNUM_TARGET_GLES
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<2, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<3, Double>&);
-template Corrade::Utility::Debug operator<<(Corrade::Utility::Debug, const Vector<4, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<2, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<3, Double>&);
+template Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Vector<4, Double>&);
 #endif
 #endif
 
diff --git a/src/Magnum/Mesh.cpp b/src/Magnum/Mesh.cpp
index 57e85b97b..acf2917d6 100644
--- a/src/Magnum/Mesh.cpp
+++ b/src/Magnum/Mesh.cpp
@@ -635,7 +635,7 @@ void Mesh::drawElementsInstancedImplementationNV(const GLsizei count, const GLin
 #endif
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, MeshPrimitive value) {
+Debug& operator<<(Debug& debug, MeshPrimitive value) {
     switch(value) {
         #define _c(value) case MeshPrimitive::value: return debug << "MeshPrimitive::" #value;
         _c(Points)
@@ -660,7 +660,7 @@ Debug operator<<(Debug debug, MeshPrimitive value) {
     return debug << "MeshPrimitive::(invalid)";
 }
 
-Debug operator<<(Debug debug, Mesh::IndexType value) {
+Debug& operator<<(Debug& debug, Mesh::IndexType value) {
     switch(value) {
         #define _c(value) case Mesh::IndexType::value: return debug << "Mesh::IndexType::" #value;
         _c(UnsignedByte)
diff --git a/src/Magnum/Mesh.h b/src/Magnum/Mesh.h
index 4d30ea2b1..b28d53861 100644
--- a/src/Magnum/Mesh.h
+++ b/src/Magnum/Mesh.h
@@ -1018,10 +1018,10 @@ class MAGNUM_EXPORT Mesh: public AbstractObject {
 };
 
 /** @debugoperatorenum{Magnum::MeshPrimitive} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, MeshPrimitive value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, MeshPrimitive value);
 
 /** @debugoperatorclassenum{Magnum::Mesh,Magnum::Mesh::IndexType} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Mesh::IndexType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Mesh::IndexType value);
 
 inline GLuint Mesh::release() {
     const GLuint id = _id;
diff --git a/src/Magnum/PixelFormat.cpp b/src/Magnum/PixelFormat.cpp
index 20953520c..226b6295a 100644
--- a/src/Magnum/PixelFormat.cpp
+++ b/src/Magnum/PixelFormat.cpp
@@ -30,7 +30,7 @@
 namespace Magnum {
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const PixelFormat value) {
+Debug& operator<<(Debug& debug, const PixelFormat value) {
     switch(value) {
         #define _c(value) case PixelFormat::value: return debug << "PixelFormat::" #value;
         #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
@@ -82,7 +82,7 @@ Debug operator<<(Debug debug, const PixelFormat value) {
     return debug << "PixelFormat::(invalid)";
 }
 
-Debug operator<<(Debug debug, const PixelType value) {
+Debug& operator<<(Debug& debug, const PixelType value) {
     switch(value) {
         #define _c(value) case PixelType::value: return debug << "PixelType::" #value;
         _c(UnsignedByte)
@@ -137,7 +137,7 @@ Debug operator<<(Debug debug, const PixelType value) {
     return debug << "PixelType::(invalid)";
 }
 
-Debug operator<<(Debug debug, const CompressedPixelFormat value) {
+Debug& operator<<(Debug& debug, const CompressedPixelFormat value) {
     switch(value) {
         #define _c(value) case CompressedPixelFormat::value: return debug << "CompressedPixelFormat::" #value;
         #ifndef MAGNUM_TARGET_GLES
diff --git a/src/Magnum/PixelFormat.h b/src/Magnum/PixelFormat.h
index a191478cb..df6a44cd5 100644
--- a/src/Magnum/PixelFormat.h
+++ b/src/Magnum/PixelFormat.h
@@ -1193,13 +1193,13 @@ enum class CompressedPixelFormat: GLenum {
 };
 
 /** @debugoperatorenum{Magnum::PixelFormat} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, PixelFormat value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, PixelFormat value);
 
 /** @debugoperatorenum{Magnum::PixelType} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, PixelType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, PixelType value);
 
 /** @debugoperatorenum{Magnum::CompressedPixelFormat} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, CompressedPixelFormat value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, CompressedPixelFormat value);
 
 }
 
diff --git a/src/Magnum/Renderer.cpp b/src/Magnum/Renderer.cpp
index 8b146a959..87222fbf6 100644
--- a/src/Magnum/Renderer.cpp
+++ b/src/Magnum/Renderer.cpp
@@ -238,7 +238,7 @@ Renderer::GraphicsResetStatus Renderer::graphicsResetStatusImplementationRobustn
 #endif
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const Renderer::Error value) {
+Debug& operator<<(Debug& debug, const Renderer::Error value) {
     switch(value) {
         #define _c(value) case Renderer::Error::value: return debug << "Renderer::Error::" #value;
         _c(NoError)
@@ -258,7 +258,7 @@ Debug operator<<(Debug debug, const Renderer::Error value) {
 }
 
 #ifndef MAGNUM_TARGET_WEBGL
-Debug operator<<(Debug debug, const Renderer::ResetNotificationStrategy value) {
+Debug& operator<<(Debug& debug, const Renderer::ResetNotificationStrategy value) {
     switch(value) {
         #define _c(value) case Renderer::ResetNotificationStrategy::value: return debug << "Renderer::ResetNotificationStrategy::" #value;
         _c(NoResetNotification)
@@ -269,7 +269,7 @@ Debug operator<<(Debug debug, const Renderer::ResetNotificationStrategy value) {
     return debug << "Renderer::ResetNotificationStrategy::(invalid)";
 }
 
-Debug operator<<(Debug debug, const Renderer::GraphicsResetStatus value) {
+Debug& operator<<(Debug& debug, const Renderer::GraphicsResetStatus value) {
     switch(value) {
         #define _c(value) case Renderer::GraphicsResetStatus::value: return debug << "Renderer::GraphicsResetStatus::" #value;
         _c(NoError)
diff --git a/src/Magnum/Renderer.h b/src/Magnum/Renderer.h
index 412167f3d..e7bddd740 100644
--- a/src/Magnum/Renderer.h
+++ b/src/Magnum/Renderer.h
@@ -1436,14 +1436,14 @@ class MAGNUM_EXPORT Renderer {
 };
 
 /** @debugoperatorclassenum{Magnum::Renderer,Magnum::Renderer::Error} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Renderer::Error value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Renderer::Error value);
 
 #ifndef MAGNUM_TARGET_WEBGL
 /** @debugoperatorclassenum{Magnum::Renderer,Magnum::Renderer::ResetNotificationStrategy} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Renderer::ResetNotificationStrategy value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Renderer::ResetNotificationStrategy value);
 
 /** @debugoperatorclassenum{Magnum::Renderer,Magnum::Renderer::GraphicsResetStatus} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Renderer::GraphicsResetStatus value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Renderer::GraphicsResetStatus value);
 #endif
 
 }
diff --git a/src/Magnum/Resource.cpp b/src/Magnum/Resource.cpp
index fea4895e3..2fc5c9d11 100644
--- a/src/Magnum/Resource.cpp
+++ b/src/Magnum/Resource.cpp
@@ -28,7 +28,7 @@
 namespace Magnum {
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug MAGNUM_EXPORT operator<<(Debug debug, ResourceState value) {
+Debug& operator<<(Debug& debug, const ResourceState value) {
     switch(value) {
         #define _c(value) case ResourceState::value: return debug << "ResourceState::" #value;
         _c(NotLoaded)
diff --git a/src/Magnum/Resource.h b/src/Magnum/Resource.h
index 94c51a823..7738c8d2a 100644
--- a/src/Magnum/Resource.h
+++ b/src/Magnum/Resource.h
@@ -69,7 +69,7 @@ enum class ResourceState: UnsignedByte {
 };
 
 /** @debugoperatorenum{Magnum::ResourceState} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, ResourceState value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, ResourceState value);
 
 /**
 @brief Key for accessing resource
@@ -100,7 +100,7 @@ class ResourceKey: public Utility::MurmurHash2::Digest {
 };
 
 /** @debugoperator{Magnum::ResourceKey} */
-inline Debug operator<<(Debug debug, const ResourceKey& value) {
+inline Debug& operator<<(Debug& debug, const ResourceKey& value) {
     return debug << static_cast<const Utility::HashDigest<sizeof(std::size_t)>&>(value);
 }
 
diff --git a/src/Magnum/Sampler.cpp b/src/Magnum/Sampler.cpp
index 39e3f8838..d9ebb810d 100644
--- a/src/Magnum/Sampler.cpp
+++ b/src/Magnum/Sampler.cpp
@@ -61,7 +61,7 @@ Float Sampler::maxMaxAnisotropy() {
 }
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const Sampler::Filter value) {
+Debug& operator<<(Debug& debug, const Sampler::Filter value) {
     switch(value) {
         #define _c(value) case Sampler::Filter::value: return debug << "Sampler::Filter::" #value;
         _c(Nearest)
@@ -72,7 +72,7 @@ Debug operator<<(Debug debug, const Sampler::Filter value) {
     return debug << "Sampler::Filter::(invalid)";
 }
 
-Debug operator<<(Debug debug, const Sampler::Mipmap value) {
+Debug& operator<<(Debug& debug, const Sampler::Mipmap value) {
     switch(value) {
         #define _c(value) case Sampler::Mipmap::value: return debug << "Sampler::Mipmap::" #value;
         _c(Base)
@@ -84,7 +84,7 @@ Debug operator<<(Debug debug, const Sampler::Mipmap value) {
     return debug << "Sampler::Mipmap::(invalid)";
 }
 
-Debug operator<<(Debug debug, const Sampler::Wrapping value) {
+Debug& operator<<(Debug& debug, const Sampler::Wrapping value) {
     switch(value) {
         #define _c(value) case Sampler::Wrapping::value: return debug << "Sampler::Wrapping::" #value;
         _c(Repeat)
@@ -103,7 +103,7 @@ Debug operator<<(Debug debug, const Sampler::Wrapping value) {
 }
 
 #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
-Debug operator<<(Debug debug, const Sampler::CompareMode value) {
+Debug& operator<<(Debug& debug, const Sampler::CompareMode value) {
     switch(value) {
         #define _c(value) case Sampler::CompareMode::value: return debug << "Sampler::CompareMode::" #value;
         _c(None)
@@ -114,7 +114,7 @@ Debug operator<<(Debug debug, const Sampler::CompareMode value) {
     return debug << "Sampler::CompareFunction::(invalid)";
 }
 
-Debug operator<<(Debug debug, const Sampler::CompareFunction value) {
+Debug& operator<<(Debug& debug, const Sampler::CompareFunction value) {
     switch(value) {
         #define _c(value) case Sampler::CompareFunction::value: return debug << "Sampler::CompareFunction::" #value;
         _c(Never)
@@ -133,7 +133,7 @@ Debug operator<<(Debug debug, const Sampler::CompareFunction value) {
 #endif
 
 #ifndef MAGNUM_TARGET_GLES
-Debug operator<<(Debug debug, const Sampler::DepthStencilMode value) {
+Debug& operator<<(Debug& debug, const Sampler::DepthStencilMode value) {
     switch(value) {
         #define _c(value) case Sampler::DepthStencilMode::value: return debug << "Sampler::DepthStencilMode::" #value;
         _c(DepthComponent)
diff --git a/src/Magnum/Sampler.h b/src/Magnum/Sampler.h
index 9705582cb..3e71bc240 100644
--- a/src/Magnum/Sampler.h
+++ b/src/Magnum/Sampler.h
@@ -256,25 +256,25 @@ class MAGNUM_EXPORT Sampler {
 };
 
 /** @debugoperatorclassenum{Magnum::Sampler,Magnum::Sampler::Filter} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Sampler::Filter value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Sampler::Filter value);
 
 /** @debugoperatorclassenum{Magnum::Sampler,Magnum::Sampler::Mipmap} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Sampler::Mipmap value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Sampler::Mipmap value);
 
 /** @debugoperatorclassenum{Magnum::Sampler,Magnum::Sampler::Wrapping} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Sampler::Wrapping value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Sampler::Wrapping value);
 
 #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
 /** @debugoperatorclassenum{Magnum::Sampler,Magnum::Sampler::CompareMode} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Sampler::CompareMode value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Sampler::CompareMode value);
 
 /** @debugoperatorclassenum{Magnum::Sampler,Magnum::Sampler::CompareFunction} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Sampler::CompareFunction value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Sampler::CompareFunction value);
 #endif
 
 #ifndef MAGNUM_TARGET_GLES
 /** @debugoperatorclassenum{Magnum::Sampler,Magnum::Sampler::DepthStencilMode} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Sampler::DepthStencilMode value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Sampler::DepthStencilMode value);
 #endif
 
 }
diff --git a/src/Magnum/SceneGraph/Animable.cpp b/src/Magnum/SceneGraph/Animable.cpp
index 628e51a88..7e537e387 100644
--- a/src/Magnum/SceneGraph/Animable.cpp
+++ b/src/Magnum/SceneGraph/Animable.cpp
@@ -29,7 +29,7 @@
 
 namespace Magnum { namespace SceneGraph {
 
-Debug operator<<(Debug debug, AnimationState value) {
+Debug& operator<<(Debug& debug, AnimationState value) {
     switch(value) {
         #define _c(value) case AnimationState::value: return debug << "SceneGraph::AnimationState::" #value;
         _c(Stopped)
diff --git a/src/Magnum/SceneGraph/Animable.h b/src/Magnum/SceneGraph/Animable.h
index e39c462d3..4e1df2a3c 100644
--- a/src/Magnum/SceneGraph/Animable.h
+++ b/src/Magnum/SceneGraph/Animable.h
@@ -57,7 +57,7 @@ enum class AnimationState: UnsignedByte {
 };
 
 /** @debugoperatorenum{Magnum::SceneGraph::AnimationState} */
-Debug MAGNUM_SCENEGRAPH_EXPORT operator<<(Debug debug, AnimationState value);
+MAGNUM_SCENEGRAPH_EXPORT Debug& operator<<(Debug& debug, AnimationState value);
 
 /**
 @brief Animable
diff --git a/src/Magnum/Shader.cpp b/src/Magnum/Shader.cpp
index ccdbdc3c3..21850f51a 100644
--- a/src/Magnum/Shader.cpp
+++ b/src/Magnum/Shader.cpp
@@ -898,7 +898,7 @@ bool Shader::compile(std::initializer_list<std::reference_wrapper<Shader>> shade
 }
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const Shader::Type value) {
+Debug& operator<<(Debug& debug, const Shader::Type value) {
     switch(value) {
         #define _c(value) case Shader::Type::value: return debug << "Shader::Type::" #value;
         _c(Vertex)
diff --git a/src/Magnum/Shader.h b/src/Magnum/Shader.h
index 0bfdaafd7..146debd7f 100644
--- a/src/Magnum/Shader.h
+++ b/src/Magnum/Shader.h
@@ -630,7 +630,7 @@ class MAGNUM_EXPORT Shader: public AbstractObject {
 };
 
 /** @debugoperatorclassenum{Magnum::Shader,Magnum::Shader::Type} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Shader::Type value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Shader::Type value);
 
 inline Shader::Shader(Shader&& other) noexcept: _type(other._type), _id(other._id), _sources(std::move(other._sources)) {
     other._id = 0;
diff --git a/src/Magnum/Shapes/Composition.h b/src/Magnum/Shapes/Composition.h
index 881d17566..a54d5e1b8 100644
--- a/src/Magnum/Shapes/Composition.h
+++ b/src/Magnum/Shapes/Composition.h
@@ -195,7 +195,7 @@ typedef Composition<3> Composition3D;
 
 #ifdef DOXYGEN_GENERATING_OUTPUT
 /** @debugoperatorclassenum{Magnum::Shapes::Composition,Magnum::Shapes::Composition::Type} */
-template<UnsignedInt dimensions> Debug operator<<(Debug debug, typename Composition<dimensions>::Type value);
+template<UnsignedInt dimensions> Debug& operator<<(Debug& debug, typename Composition<dimensions>::Type value);
 #endif
 
 /** @relates Composition
diff --git a/src/Magnum/Shapes/shapeImplementation.cpp b/src/Magnum/Shapes/shapeImplementation.cpp
index 07614c514..ef70c149b 100644
--- a/src/Magnum/Shapes/shapeImplementation.cpp
+++ b/src/Magnum/Shapes/shapeImplementation.cpp
@@ -29,7 +29,7 @@
 
 namespace Magnum { namespace Shapes { namespace Implementation {
 
-Debug operator<<(Debug debug, ShapeDimensionTraits<2>::Type value) {
+Debug& operator<<(Debug& debug, ShapeDimensionTraits<2>::Type value) {
     switch(value) {
         #define _val(value) case ShapeDimensionTraits<2>::Type::value: return debug << "Shapes::Shape2D::Type::" #value;
         _val(Point)
@@ -48,7 +48,7 @@ Debug operator<<(Debug debug, ShapeDimensionTraits<2>::Type value) {
     return debug << "Shapes::Shape2D::Type::(unknown)";
 }
 
-Debug operator<<(Debug debug, ShapeDimensionTraits<3>::Type value) {
+Debug& operator<<(Debug& debug, ShapeDimensionTraits<3>::Type value) {
     switch(value) {
         #define _val(value) case ShapeDimensionTraits<3>::Type::value: return debug << "Shapes::Shape3D::Type::" #value;
         _val(Point)
diff --git a/src/Magnum/Shapes/shapeImplementation.h b/src/Magnum/Shapes/shapeImplementation.h
index 80213fed0..170172188 100644
--- a/src/Magnum/Shapes/shapeImplementation.h
+++ b/src/Magnum/Shapes/shapeImplementation.h
@@ -87,8 +87,8 @@ template<> struct ShapeDimensionTraits<3> {
     };
 };
 
-Debug MAGNUM_SHAPES_EXPORT operator<<(Debug debug, ShapeDimensionTraits<2>::Type value);
-Debug MAGNUM_SHAPES_EXPORT operator<<(Debug debug, ShapeDimensionTraits<3>::Type value);
+MAGNUM_SHAPES_EXPORT Debug& operator<<(Debug& debug, ShapeDimensionTraits<2>::Type value);
+MAGNUM_SHAPES_EXPORT Debug& operator<<(Debug& debug, ShapeDimensionTraits<3>::Type value);
 
 /* Enum value corresponding to given type */
 
diff --git a/src/Magnum/Trade/AbstractMaterialData.cpp b/src/Magnum/Trade/AbstractMaterialData.cpp
index a00cd0933..e4f7475b8 100644
--- a/src/Magnum/Trade/AbstractMaterialData.cpp
+++ b/src/Magnum/Trade/AbstractMaterialData.cpp
@@ -33,7 +33,7 @@ AbstractMaterialData::AbstractMaterialData(MaterialType type): _type(type) {}
 
 AbstractMaterialData::~AbstractMaterialData() {}
 
-Debug operator<<(Debug debug, const MaterialType value) {
+Debug& operator<<(Debug& debug, const MaterialType value) {
     switch(value) {
         #define _c(value) case MaterialType::value: return debug << "Trade::MaterialType::" #value;
         _c(Phong)
diff --git a/src/Magnum/Trade/AbstractMaterialData.h b/src/Magnum/Trade/AbstractMaterialData.h
index 1b8d1a88c..474e40b7f 100644
--- a/src/Magnum/Trade/AbstractMaterialData.h
+++ b/src/Magnum/Trade/AbstractMaterialData.h
@@ -79,7 +79,7 @@ class MAGNUM_EXPORT AbstractMaterialData {
 };
 
 /** @debugoperatorenum{Magnum::Trade::MaterialType} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, MaterialType value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, MaterialType value);
 
 }}
 
diff --git a/src/Magnum/Trade/ObjectData2D.cpp b/src/Magnum/Trade/ObjectData2D.cpp
index a360ecc54..28152878e 100644
--- a/src/Magnum/Trade/ObjectData2D.cpp
+++ b/src/Magnum/Trade/ObjectData2D.cpp
@@ -38,7 +38,7 @@ ObjectData2D::~ObjectData2D() = default;
 ObjectData2D& ObjectData2D::operator=(ObjectData2D&&) = default;
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, ObjectInstanceType2D value) {
+Debug& operator<<(Debug& debug, ObjectInstanceType2D value) {
     switch(value) {
         #define _c(value) case ObjectInstanceType2D::value: return debug << "Trade::ObjectInstanceType2D::" #value;
         _c(Camera)
diff --git a/src/Magnum/Trade/ObjectData2D.h b/src/Magnum/Trade/ObjectData2D.h
index 58125f5b5..cd56be741 100644
--- a/src/Magnum/Trade/ObjectData2D.h
+++ b/src/Magnum/Trade/ObjectData2D.h
@@ -121,7 +121,7 @@ class MAGNUM_EXPORT ObjectData2D {
 };
 
 /** @debugoperatorenum{Magnum::Trade::ObjectInstanceType2D} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, ObjectInstanceType2D value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, ObjectInstanceType2D value);
 
 }}
 
diff --git a/src/Magnum/Trade/ObjectData3D.cpp b/src/Magnum/Trade/ObjectData3D.cpp
index c098e7498..2f1737193 100644
--- a/src/Magnum/Trade/ObjectData3D.cpp
+++ b/src/Magnum/Trade/ObjectData3D.cpp
@@ -38,7 +38,7 @@ ObjectData3D::~ObjectData3D() = default;
 ObjectData3D& ObjectData3D::operator=(ObjectData3D&&) = default;
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, ObjectInstanceType3D value) {
+Debug& operator<<(Debug& debug, ObjectInstanceType3D value) {
     switch(value) {
         #define _c(value) case ObjectInstanceType3D::value: return debug << "Trade::ObjectInstanceType3D::" #value;
         _c(Camera)
diff --git a/src/Magnum/Trade/ObjectData3D.h b/src/Magnum/Trade/ObjectData3D.h
index b8f1ca7f9..679611152 100644
--- a/src/Magnum/Trade/ObjectData3D.h
+++ b/src/Magnum/Trade/ObjectData3D.h
@@ -123,7 +123,7 @@ class MAGNUM_EXPORT ObjectData3D {
 };
 
 /** @debugoperatorenum{Magnum::Trade::ObjectInstanceType3D} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, ObjectInstanceType3D value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, ObjectInstanceType3D value);
 
 }}
 
diff --git a/src/Magnum/Trade/TextureData.cpp b/src/Magnum/Trade/TextureData.cpp
index bcfdbd39e..4120e99ac 100644
--- a/src/Magnum/Trade/TextureData.cpp
+++ b/src/Magnum/Trade/TextureData.cpp
@@ -28,7 +28,7 @@
 namespace Magnum { namespace Trade {
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, const TextureData::Type value) {
+Debug& operator<<(Debug& debug, const TextureData::Type value) {
     switch(value) {
         #define _c(value) case TextureData::Type::value: return debug << "Trade::TextureData::Type::" #value;
         _c(Texture1D)
diff --git a/src/Magnum/Trade/TextureData.h b/src/Magnum/Trade/TextureData.h
index e703991dd..89dca1998 100644
--- a/src/Magnum/Trade/TextureData.h
+++ b/src/Magnum/Trade/TextureData.h
@@ -110,7 +110,7 @@ class TextureData {
 };
 
 /** @debugoperatorclassenum{Magnum::Trade::TextureData,Magnum::Trade::TextureData::Type} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, TextureData::Type value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, TextureData::Type value);
 
 }}
 
diff --git a/src/Magnum/Version.cpp b/src/Magnum/Version.cpp
index 18b1dc0f3..ca4ff2696 100644
--- a/src/Magnum/Version.cpp
+++ b/src/Magnum/Version.cpp
@@ -30,7 +30,7 @@
 namespace Magnum {
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-Debug operator<<(Debug debug, Version value) {
+Debug& operator<<(Debug& debug, Version value) {
     switch(value) {
         #define _c(value, string) case Version::value: return debug << string;
         _c(None, "None")
diff --git a/src/Magnum/Version.h b/src/Magnum/Version.h
index 37f951b62..37515ae12 100644
--- a/src/Magnum/Version.h
+++ b/src/Magnum/Version.h
@@ -110,7 +110,7 @@ inline std::pair<Int, Int> version(Version version) {
 }
 
 /** @debugoperatorenum{Magnum::Version} */
-Debug MAGNUM_EXPORT operator<<(Debug debug, Version value);
+MAGNUM_EXPORT Debug& operator<<(Debug& debug, Version value);
 
 }