diff --git a/src/Math/Matrix.h b/src/Math/Matrix.h
index a1f205336..2f4f2d9df 100644
--- a/src/Math/Matrix.h
+++ b/src/Math/Matrix.h
@@ -232,7 +232,7 @@ template<class T> class Matrix<T, 2> {
 #endif
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template<class T, size_t size> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Matrix<T, size>& value) {
+template<class T, size_t size> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Matrix<T, size>& value) {
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << "Matrix(";
     for(size_t row = 0; row != size; ++row) {
diff --git a/src/Math/Matrix3.h b/src/Math/Matrix3.h
index 0addd669d..e4c7fe05c 100644
--- a/src/Math/Matrix3.h
+++ b/src/Math/Matrix3.h
@@ -59,7 +59,7 @@ template<class T> class Matrix3: public Matrix<T, 3> {
 };
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Matrix3<T>& value) {
+template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Matrix3<T>& value) {
     return debug << static_cast<const Magnum::Math::Matrix<T, 3>&>(value);
 }
 #endif
diff --git a/src/Math/Matrix4.h b/src/Math/Matrix4.h
index f80dc38bc..a5a24649a 100644
--- a/src/Math/Matrix4.h
+++ b/src/Math/Matrix4.h
@@ -162,7 +162,7 @@ template<class T> class Matrix4: public Matrix<T, 4> {
 };
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Matrix4<T>& value) {
+template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Matrix4<T>& value) {
     return debug << static_cast<const Magnum::Math::Matrix<T, 4>&>(value);
 }
 #endif
diff --git a/src/Math/Vector.h b/src/Math/Vector.h
index 2ec7dec93..c866350da 100644
--- a/src/Math/Vector.h
+++ b/src/Math/Vector.h
@@ -178,7 +178,7 @@ template<class T, size_t size> class Vector {
 };
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template<class T, size_t size> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector<T, size>& value) {
+template<class T, size_t size> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector<T, size>& value) {
     debug.setFlag(Corrade::Utility::Debug::SpaceAfterEachValue, false);
     debug << "Vector(";
     for(size_t i = 0; i != size; ++i) {
diff --git a/src/Math/Vector2.h b/src/Math/Vector2.h
index 03388ce83..91ededf27 100644
--- a/src/Math/Vector2.h
+++ b/src/Math/Vector2.h
@@ -76,7 +76,7 @@ template<class T> class Vector2: public Vector<T, 2> {
 };
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector2<T>& value) {
+template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector2<T>& value) {
     return debug << static_cast<const Magnum::Math::Vector<T, 2>&>(value);
 }
 #endif
diff --git a/src/Math/Vector3.h b/src/Math/Vector3.h
index bfdee4f1a..0f4767014 100644
--- a/src/Math/Vector3.h
+++ b/src/Math/Vector3.h
@@ -112,7 +112,7 @@ template<class T> class Vector3: public Vector<T, 3> {
 };
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector3<T>& value) {
+template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector3<T>& value) {
     return debug << static_cast<const Magnum::Math::Vector<T, 3>&>(value);
 }
 #endif
diff --git a/src/Math/Vector4.h b/src/Math/Vector4.h
index 0e62de8b8..47cfb5645 100644
--- a/src/Math/Vector4.h
+++ b/src/Math/Vector4.h
@@ -119,7 +119,7 @@ template<class T> class Vector4: public Vector<T, 4> {
 };
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
-template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector4<T>& value) {
+template<class T> Corrade::Utility::Debug operator<<(Corrade::Utility::Debug debug, const Magnum::Math::Vector4<T>& value) {
     return debug << static_cast<const Magnum::Math::Vector<T, 4>&>(value);
 }
 #endif