diff --git a/src/Magnum/AbstractFramebuffer.cpp b/src/Magnum/AbstractFramebuffer.cpp
index b57f6597a..f205c4f2d 100644
--- a/src/Magnum/AbstractFramebuffer.cpp
+++ b/src/Magnum/AbstractFramebuffer.cpp
@@ -140,16 +140,28 @@ void AbstractFramebuffer::blit(AbstractFramebuffer& source, AbstractFramebuffer&
 }
 
 #ifdef MAGNUM_TARGET_GLES2
-void AbstractFramebuffer::blitImplementationANGLE(const Range2Di&, const Range2Di&, FramebufferBlitMask, FramebufferBlitFilter) {
-    /** @todo Re-enable when extension loader is available for ES */
-    CORRADE_INTERNAL_ASSERT(false);
-    //glBlitFramebufferANGLE(sourceRectangle.left(), sourceRectangle.bottom(), sourceRectangle.right(), sourceRectangle.top(), destinationRectangle.left(), destinationRectangle.bottom(), destinationRectangle.right(), destinationRectangle.top(), GLbitfield(mask), GLenum(filter));
+void AbstractFramebuffer::blitImplementationANGLE(const Range2Di& sourceRectangle, const Range2Di& destinationRectangle, const FramebufferBlitMask mask, const FramebufferBlitFilter filter) {
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glBlitFramebufferANGLE(sourceRectangle.left(), sourceRectangle.bottom(), sourceRectangle.right(), sourceRectangle.top(), destinationRectangle.left(), destinationRectangle.bottom(), destinationRectangle.right(), destinationRectangle.top(), GLbitfield(mask), GLenum(filter));
+    #else
+    static_cast<void>(sourceRectangle);
+    static_cast<void>(destinationRectangle);
+    static_cast<void>(mask);
+    static_cast<void>(filter);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
-void AbstractFramebuffer::blitImplementationNV(const Range2Di&, const Range2Di&, FramebufferBlitMask, FramebufferBlitFilter) {
-    /** @todo Re-enable when extension loader is available for ES */
-    CORRADE_INTERNAL_ASSERT(false);
-    //glBlitFramebufferNV(sourceRectangle.left(), sourceRectangle.bottom(), sourceRectangle.right(), sourceRectangle.top(), destinationRectangle.left(), destinationRectangle.bottom(), destinationRectangle.right(), destinationRectangle.top(), GLbitfield(mask), GLenum(filter));
+void AbstractFramebuffer::blitImplementationNV(const Range2Di& sourceRectangle, const Range2Di& destinationRectangle, const FramebufferBlitMask mask, const FramebufferBlitFilter filter) {
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glBlitFramebufferNV(sourceRectangle.left(), sourceRectangle.bottom(), sourceRectangle.right(), sourceRectangle.top(), destinationRectangle.left(), destinationRectangle.bottom(), destinationRectangle.right(), destinationRectangle.top(), GLbitfield(mask), GLenum(filter));
+    #else
+    static_cast<void>(sourceRectangle);
+    static_cast<void>(destinationRectangle);
+    static_cast<void>(mask);
+    static_cast<void>(filter);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 #endif
 
@@ -218,14 +230,14 @@ void AbstractFramebuffer::read(const Vector2i& offset, const Vector2i& size, Buf
 void AbstractFramebuffer::invalidateImplementationNoOp(GLsizei, const GLenum* const) {}
 
 void AbstractFramebuffer::invalidateImplementationDefault(const GLsizei count, const GLenum* const attachments) {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glInvalidateFramebuffer(GLenum(bindInternal()), count, attachments);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDiscardFramebufferEXT(GLenum(bindInternal()), count, attachments);
     #else
     static_cast<void>(count);
     static_cast<void>(attachments);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glDiscardFramebufferEXT(GLenum(bindInternal()), count, attachments);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -249,17 +261,20 @@ GLenum AbstractFramebuffer::checkStatusImplementationDSA(const FramebufferTarget
 #endif
 
 void AbstractFramebuffer::drawBuffersImplementationDefault(GLsizei count, const GLenum* buffers) {
-    /** @todo Re-enable when extension loader is available for ES */
-    #ifndef MAGNUM_TARGET_GLES2
     #ifndef MAGNUM_TARGET_GLES2
     bindInternal(FramebufferTarget::Draw);
     #else
-    bindInternal(drawTarget);
+    bindInternal(Context::current()->state().framebuffer->drawTarget);
     #endif
+
+    #ifndef MAGNUM_TARGET_GLES2
     glDrawBuffers(count, buffers);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawBuffersNV(count, buffers);
     #else
     static_cast<void>(count);
     static_cast<void>(buffers);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -270,22 +285,21 @@ void AbstractFramebuffer::drawBuffersImplementationDSA(GLsizei count, const GLen
 #endif
 
 void AbstractFramebuffer::drawBufferImplementationDefault(GLenum buffer) {
-    /** @todo Re-enable when extension loader is available for ES */
-    #ifndef MAGNUM_TARGET_GLES2
     #ifndef MAGNUM_TARGET_GLES2
     bindInternal(FramebufferTarget::Draw);
     #else
-    bindInternal(drawTarget);
+    bindInternal(Context::current()->state().framebuffer->drawTarget);
     #endif
-    #ifndef MAGNUM_TARGET_GLES3
+
+    #ifndef MAGNUM_TARGET_GLES
     glDrawBuffer(buffer);
-    #else
+    #elif !defined(MAGNUM_TARGET_GLES2)
     glDrawBuffers(1, &buffer);
-    #endif
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawBuffersNV(1, &buffer);
     #else
     static_cast<void>(buffer);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glDrawBuffersNV(1, &buffer);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -296,18 +310,19 @@ void AbstractFramebuffer::drawBufferImplementationDSA(GLenum buffer) {
 #endif
 
 void AbstractFramebuffer::readBufferImplementationDefault(GLenum buffer) {
-    /** @todo Re-enable when extension loader is available for ES */
-    #ifndef MAGNUM_TARGET_GLES2
     #ifndef MAGNUM_TARGET_GLES2
     bindInternal(FramebufferTarget::Read);
     #else
-    bindInternal(readTarget);
+    bindInternal(Context::current()->state().framebuffer->readTarget);
     #endif
+
+    #ifndef MAGNUM_TARGET_GLES2
     glReadBuffer(buffer);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glReadBufferNV(buffer);
     #else
     static_cast<void>(buffer);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glReadBufferNV(buffer);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -322,9 +337,10 @@ void AbstractFramebuffer::readImplementationDefault(const Vector2i& offset, cons
 }
 
 void AbstractFramebuffer::readImplementationRobustness(const Vector2i& offset, const Vector2i& size, const ColorFormat format, const ColorType type, const std::size_t dataSize, GLvoid* const data) {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     glReadnPixelsARB(offset.x(), offset.y(), size.x(), size.y(), GLenum(format), GLenum(type), dataSize, data);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glReadnPixelsEXT(offset.x(), offset.y(), size.x(), size.y(), GLenum(format), GLenum(type), dataSize, data);
     #else
     static_cast<void>(offset);
     static_cast<void>(size);
@@ -332,8 +348,7 @@ void AbstractFramebuffer::readImplementationRobustness(const Vector2i& offset, c
     static_cast<void>(type);
     static_cast<void>(dataSize);
     static_cast<void>(data);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glReadnPixelsEXT(offset.x(), offset.y(), size.x(), size.y(), GLenum(format), GLenum(type), data);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
diff --git a/src/Magnum/AbstractObject.cpp b/src/Magnum/AbstractObject.cpp
index 0b07d3c8f..e59038394 100644
--- a/src/Magnum/AbstractObject.cpp
+++ b/src/Magnum/AbstractObject.cpp
@@ -36,6 +36,7 @@
 
 namespace Magnum {
 
+#if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
 namespace {
     inline GLenum extTypeFromKhrIdentifier(GLenum khrIdentifier) {
         switch(khrIdentifier) {
@@ -106,6 +107,7 @@ namespace {
         CORRADE_ASSERT_UNREACHABLE();
     }
 }
+#endif
 
 Int AbstractObject::maxLabelLength() {
     if(!Context::current()->isExtensionSupported<Extensions::GL::KHR::debug>())
@@ -127,28 +129,27 @@ Int AbstractObject::maxLabelLength() {
 void AbstractObject::labelImplementationNoOp(GLenum, GLuint, Containers::ArrayReference<const char>) {}
 
 void AbstractObject::labelImplementationKhr(const GLenum identifier, const GLuint name, const Containers::ArrayReference<const char> label) {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     glObjectLabel(identifier, name, label.size(), label);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glObjectLabelKHR(identifier, name, label.size(), label);
     #else
     static_cast<void>(identifier);
     static_cast<void>(name);
     static_cast<void>(label);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glObjectLabelKHR(identifier, name, label.size(), label);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
 void AbstractObject::labelImplementationExt(const GLenum identifier, const GLuint name, const Containers::ArrayReference<const char> label) {
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
     const GLenum type = extTypeFromKhrIdentifier(identifier);
-    /** @todo Re-enable when extension loader is available for ES */
-    #ifndef MAGNUM_TARGET_GLES
     glLabelObjectEXT(type, name, label.size(), label);
     #else
-    static_cast<void>(type);
+    static_cast<void>(identifier);
     static_cast<void>(name);
     static_cast<void>(label);
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -157,24 +158,25 @@ std::string AbstractObject::getLabelImplementationNoOp(GLenum, GLuint) { return
 std::string AbstractObject::getLabelImplementationKhr(const GLenum identifier, const GLuint name) {
     /* Get label size (w/o null terminator) */
     GLsizei size;
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     glGetObjectLabel(identifier, name, 0, &size, nullptr);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glGetObjectLabelKHR(identifier, name, 0, &size, nullptr);
     #else
     static_cast<void>(identifier);
     static_cast<void>(name);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glGetObjectLabelKHR(identifier, name, 0, &size, nullptr);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 
     /* Make place also for the null terminator */
     std::string label;
     label.resize(size+1);
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     glGetObjectLabel(identifier, name, size+1, nullptr, &label[0]);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glGetObjectLabelKHR(identifier, name, size+1, nullptr, &label[0]);
     #else
-    //glGetObjectLabelKHR(identifier, name, size+1, nullptr, &label[0]);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 
     /* Pop null terminator and return the string */
@@ -183,25 +185,25 @@ std::string AbstractObject::getLabelImplementationKhr(const GLenum identifier, c
 }
 
 std::string AbstractObject::getLabelImplementationExt(const GLenum identifier, const GLuint name) {
-    const GLenum type = extTypeFromKhrIdentifier(identifier);
+    GLsizei size;
 
     /* Get label size (w/o null terminator) */
-    GLsizei size;
-    /** @todo Re-enable when extension loader is available for ES */
-    #ifndef MAGNUM_TARGET_GLES
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    const GLenum type = extTypeFromKhrIdentifier(identifier);
     glGetObjectLabelEXT(type, name, 0, &size, nullptr);
     #else
-    static_cast<void>(type);
+    static_cast<void>(identifier);
     static_cast<void>(name);
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 
     /* Make place also for the null terminator */
     std::string label;
     label.resize(size+1);
-    /** @todo Re-enable when extension loader is available for ES */
-    #ifndef MAGNUM_TARGET_GLES
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
     glGetObjectLabelEXT(identifier, name, size+1, nullptr, &label[0]);
+    #else
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 
     /* Pop null terminator and return the string */
diff --git a/src/Magnum/AbstractShaderProgram.cpp b/src/Magnum/AbstractShaderProgram.cpp
index 954dfbdd4..aed41aa27 100644
--- a/src/Magnum/AbstractShaderProgram.cpp
+++ b/src/Magnum/AbstractShaderProgram.cpp
@@ -363,15 +363,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const GLfloat* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform1fv(_id, location, count, values);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform1fvEXT(_id, location, count, values);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform1fvEXT(_id, location, count, values);
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -391,15 +391,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<2, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform2fv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform2fvEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform2fvEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -419,15 +419,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<3, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform3fv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform3fvEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform3fvEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -447,15 +447,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<4, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform4fv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform4fvEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform4fvEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -475,15 +475,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const GLint* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform1iv(_id, location, count, values);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform1ivEXT(_id, location, count, values);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform1ivEXT(_id, location, count, values);
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -503,15 +503,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<2, GLint>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform2iv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform2ivEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform2ivEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -531,15 +531,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<3, GLint>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform3iv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform3ivEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform3ivEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -559,15 +559,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<4, GLint>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform4iv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform4ivEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform4ivEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -588,15 +588,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const GLuint* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform1uiv(_id, location, count, values);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform1uivEXT(_id, location, count, values);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform1uivEXT(_id, location, count, values);
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -616,15 +616,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<2, GLuint>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform2uiv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform2uivEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform2uivEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -644,15 +644,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<3, GLuint>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform3uiv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform3uivEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform3uivEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -672,15 +672,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::Vector<4, GLuint>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniform4uiv(_id, location, count, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniform4uivEXT(_id, location, count, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniform4uivEXT(_id, location, count, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -771,15 +771,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<2, 2, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix2fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix2fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix2fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -799,15 +799,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<3, 3, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix3fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix3fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix3fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -827,15 +827,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<4, 4, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix4fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix4fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix4fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -856,15 +856,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<2, 3, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix2x3fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix2x3fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix2x3fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -884,15 +884,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<3, 2, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix3x2fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix3x2fv(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix3x2fv(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -912,15 +912,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<2, 4, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix2x4fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix2x4fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix2x4fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -940,15 +940,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<4, 2, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix4x2fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix4x2fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix4x2fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -968,15 +968,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<3, 4, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix3x4fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix3x4fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix3x4fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -996,15 +996,15 @@ void AbstractShaderProgram::uniformImplementationDefault(const GLint location, c
 }
 
 void AbstractShaderProgram::uniformImplementationSSO(const GLint location, const GLsizei count, const Math::RectangularMatrix<4, 3, GLfloat>* const values) {
-    /** @todo Enable when extension loader for ES is available */
     #ifndef MAGNUM_TARGET_GLES
     glProgramUniformMatrix4x3fv(_id, location, count, GL_FALSE, values[0].data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glProgramUniformMatrix4x3fvEXT(_id, location, count, GL_FALSE, values[0].data());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glProgramUniformMatrix4x3fvEXT(_id, location, count, GL_FALSE, values[0].data());
     static_cast<void>(location);
     static_cast<void>(count);
     static_cast<void>(values);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
diff --git a/src/Magnum/AbstractTexture.cpp b/src/Magnum/AbstractTexture.cpp
index 76b53eb78..ae381d210 100644
--- a/src/Magnum/AbstractTexture.cpp
+++ b/src/Magnum/AbstractTexture.cpp
@@ -891,16 +891,16 @@ void AbstractTexture::storageImplementationFallback(const GLenum target, const G
 
 void AbstractTexture::storageImplementationDefault(GLenum target, GLsizei levels, TextureFormat internalFormat, const Vector2i& size) {
     bindInternal();
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glTexStorage2D(target, levels, GLenum(internalFormat), size.x(), size.y());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glTexStorage2DEXT(target, levels, GLenum(internalFormat), size.x(), size.y());
     #else
     static_cast<void>(target);
     static_cast<void>(levels);
     static_cast<void>(internalFormat);
     static_cast<void>(size);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glTexStorage2DEXT(target, levels, GLenum(internalFormat), size.x(), size.y());
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -945,16 +945,16 @@ void AbstractTexture::storageImplementationFallback(GLenum target, GLsizei level
 
 void AbstractTexture::storageImplementationDefault(GLenum target, GLsizei levels, TextureFormat internalFormat, const Vector3i& size) {
     bindInternal();
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glTexStorage3D(target, levels, GLenum(internalFormat), size.x(), size.y(), size.z());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glTexStorage3DEXT(target, levels, GLenum(internalFormat), size.x(), size.y(), size.z());
     #else
     static_cast<void>(target);
     static_cast<void>(levels);
     static_cast<void>(internalFormat);
     static_cast<void>(size);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glTexStorage3DEXT(target, levels, GLenum(internalFormat), size.x(), size.y(), size.z());
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -1034,9 +1034,10 @@ void AbstractTexture::imageImplementationDSA(GLenum target, GLint level, Texture
 
 void AbstractTexture::imageImplementationDefault(GLenum target, GLint level, TextureFormat internalFormat, const Vector3i& size, ColorFormat format, ColorType type, const GLvoid* data) {
     bindInternal();
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glTexImage3D(target, level, GLint(internalFormat), size.x(), size.y(), size.z(), 0, GLenum(format), GLenum(type), data);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glTexImage3DOES(target, level, GLint(internalFormat), size.x(), size.y(), size.z(), 0, GLenum(format), GLenum(type), data);
     #else
     static_cast<void>(target);
     static_cast<void>(level);
@@ -1045,8 +1046,7 @@ void AbstractTexture::imageImplementationDefault(GLenum target, GLint level, Tex
     static_cast<void>(format);
     static_cast<void>(type);
     static_cast<void>(data);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glTexImage3DOES(target, level, GLint(internalFormat), size.x(), size.y(), size.z(), 0, GLenum(format), GLenum(type), data);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -1080,9 +1080,10 @@ void AbstractTexture::subImageImplementationDSA(GLenum target, GLint level, cons
 
 void AbstractTexture::subImageImplementationDefault(GLenum target, GLint level, const Vector3i& offset, const Vector3i& size, ColorFormat format, ColorType type, const GLvoid* data) {
     bindInternal();
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glTexSubImage3D(target, level, offset.x(), offset.y(), offset.z(), size.x(), size.y(), size.z(), GLenum(format), GLenum(type), data);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glTexSubImage3DOES(target, level, offset.x(), offset.y(), offset.z(), size.x(), size.y(), size.z(), GLenum(format), GLenum(type), data);
     #else
     static_cast<void>(target);
     static_cast<void>(level);
@@ -1091,8 +1092,7 @@ void AbstractTexture::subImageImplementationDefault(GLenum target, GLint level,
     static_cast<void>(format);
     static_cast<void>(type);
     static_cast<void>(data);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glTexSubImage3DOES(target, level, offset.x(), offset.y(), offset.z(), size.x(), size.y(), size.z(), GLenum(format), GLenum(type), data);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
diff --git a/src/Magnum/Buffer.cpp b/src/Magnum/Buffer.cpp
index 75411ae09..ff6d31e44 100644
--- a/src/Magnum/Buffer.cpp
+++ b/src/Magnum/Buffer.cpp
@@ -212,15 +212,14 @@ void* Buffer::map(const MapAccess access) {
 
 #ifdef MAGNUM_TARGET_GLES2
 void* Buffer::mapSub(const GLintptr offset, const GLsizeiptr length, const MapAccess access) {
-    /** @todo Enable also in Emscripten (?) when extension loader is available */
     #ifdef CORRADE_TARGET_NACL
     CORRADE_ASSERT(!_mappedBuffer, "Buffer::mapSub(): the buffer is already mapped", nullptr);
     return _mappedBuffer = glMapBufferSubDataCHROMIUM(GLenum(bindInternal(_targetHint)), offset, length, GLenum(access));
     #else
-    CORRADE_INTERNAL_ASSERT(false);
     static_cast<void>(offset);
     static_cast<void>(length);
     static_cast<void>(access);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 #endif
@@ -238,13 +237,12 @@ bool Buffer::unmap() { return (this->*Context::current()->state().buffer->unmapI
 
 #ifdef MAGNUM_TARGET_GLES2
 void Buffer::unmapSub() {
-    /** @todo Enable also in Emscripten (?) when extension loader is available */
     #ifdef CORRADE_TARGET_NACL
     CORRADE_ASSERT(_mappedBuffer, "Buffer::unmapSub(): the buffer is not mapped", );
     glUnmapBufferSubDataCHROMIUM(_mappedBuffer);
     _mappedBuffer = nullptr;
     #else
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 #endif
@@ -324,13 +322,13 @@ void Buffer::invalidateSubImplementationARB(GLintptr offset, GLsizeiptr length)
 #endif
 
 void* Buffer::mapImplementationDefault(MapAccess access) {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     return glMapBuffer(GLenum(bindInternal(_targetHint)), GLenum(access));
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    return glMapBufferOES(GLenum(bindInternal(_targetHint)), GLenum(access));
     #else
     static_cast<void>(access);
-    CORRADE_INTERNAL_ASSERT(false);
-    //return glMapBufferOES(GLenum(bindInternal(_targetHint)), GLenum(access));
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -341,15 +339,15 @@ void* Buffer::mapImplementationDSA(MapAccess access) {
 #endif
 
 void* Buffer::mapRangeImplementationDefault(GLintptr offset, GLsizeiptr length, MapFlags access) {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     return glMapBufferRange(GLenum(bindInternal(_targetHint)), offset, length, GLenum(access));
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    return glMapBufferRangeEXT(GLenum(bindInternal(_targetHint)), offset, length, GLenum(access));
     #else
     static_cast<void>(offset);
     static_cast<void>(length);
     static_cast<void>(access);
-    CORRADE_INTERNAL_ASSERT(false);
-    //return glMapBufferRangeEXT(GLenum(bindInternal(_targetHint)), offset, length, GLenum(access));
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -360,14 +358,14 @@ void* Buffer::mapRangeImplementationDSA(GLintptr offset, GLsizeiptr length, MapF
 #endif
 
 void Buffer::flushMappedRangeImplementationDefault(GLintptr offset, GLsizeiptr length) {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glFlushMappedBufferRange(GLenum(bindInternal(_targetHint)), offset, length);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glFlushMappedBufferRangeEXT(GLenum(bindInternal(_targetHint)), offset, length);
     #else
     static_cast<void>(offset);
     static_cast<void>(length);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glFlushMappedBufferRangeEXT(GLenum(bindInternal(_targetHint)), offset, length);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -378,12 +376,12 @@ void Buffer::flushMappedRangeImplementationDSA(GLintptr offset, GLsizeiptr lengt
 #endif
 
 bool Buffer::unmapImplementationDefault() {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     return glUnmapBuffer(GLenum(bindInternal(_targetHint)));
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    return glUnmapBufferOES(GLenum(bindInternal(_targetHint)));
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //return glUnmapBufferOES(GLenum(bindInternal(_targetHint)));
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
diff --git a/src/Magnum/DebugMessage.cpp b/src/Magnum/DebugMessage.cpp
index ef9f0685f..a444ee618 100644
--- a/src/Magnum/DebugMessage.cpp
+++ b/src/Magnum/DebugMessage.cpp
@@ -36,8 +36,7 @@ namespace Magnum {
 
 namespace {
 
-/** @todo Re-enable when extension wrangler is available for ES */
-#ifndef MAGNUM_TARGET_GLES
+#if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
 void
 #ifdef CORRADE_TARGET_WINDOWS
 APIENTRY
@@ -113,27 +112,26 @@ void DebugMessage::insertInternal(const Source source, const Type type, const Un
 void DebugMessage::insertImplementationNoOp(Source, Type, UnsignedInt, Severity, const Containers::ArrayReference<const char>) {}
 
 void DebugMessage::insertImplementationKhr(const Source source, const Type type, const UnsignedInt id, const Severity severity, const Containers::ArrayReference<const char> string) {
-    /** @todo Re-enable when extension wrangler is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     glDebugMessageInsert(GLenum(source), GLenum(type), id, GLenum(severity), string.size(), string.data());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDebugMessageInsertKHR(GLenum(source), GLenum(type), id, GLenum(severity), string.size(), string.data());
     #else
     static_cast<void>(source);
     static_cast<void>(type);
     static_cast<void>(id);
     static_cast<void>(severity);
     static_cast<void>(string);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glDebugMessageInsertEXT(GLenum(source), GLenum(type), id, GLenum(severity), string.size(), string.data());
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
 void DebugMessage::insertImplementationExt(Source, Type, UnsignedInt, Severity, const Containers::ArrayReference<const char> string) {
-    /** @todo Re-enable when extension wrangler is available for ES */
-    #ifndef MAGNUM_TARGET_GLES
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
     glInsertEventMarkerEXT(string.size(), string.data());
     #else
     static_cast<void>(string);
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -150,17 +148,17 @@ void DebugMessage::setEnabledInternal(const GLenum source, const GLenum type, co
 void DebugMessage::controlImplementationNoOp(GLenum, GLenum, GLenum, std::initializer_list<UnsignedInt>, bool) {}
 
 void DebugMessage::controlImplementationKhr(const GLenum source, const GLenum type, const GLenum severity, const std::initializer_list<UnsignedInt> ids, const bool enabled) {
-    /** @todo Re-enable when extension wrangler is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     glDebugMessageControl(source, type, severity, ids.size(), ids.begin(), enabled);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDebugMessageControlKHR(source, type, severity, ids.size(), ids.begin(), enabled);
     #else
     static_cast<void>(source);
     static_cast<void>(type);
     static_cast<void>(severity);
     static_cast<void>(ids);
     static_cast<void>(enabled);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glDebugMessageControlKHR(source, type, severity, ids.size(), ids.begin(), enabled);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -173,23 +171,23 @@ void DebugMessage::callbackImplementationKhr(const Callback callback, const void
 
     /* Adding callback */
     if(!original && callback) {
-        /** @todo Re-enable when extension wrangler is available for ES */
         #ifndef MAGNUM_TARGET_GLES
         glDebugMessageCallback(callbackWrapper, userParam);
+        #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+        glDebugMessageCallbackKHR(callbackWrapper, userParam);
         #else
         static_cast<void>(userParam);
-        CORRADE_INTERNAL_ASSERT(false);
-        //glDebugMessageCallbackEXT(callbackWrapper, userParam);
+        CORRADE_ASSERT_UNREACHABLE();
         #endif
 
     /* Deleting callback */
     } else if(original && !callback) {
-        /** @todo Re-enable when extension wrangler is available for ES */
         #ifndef MAGNUM_TARGET_GLES
         glDebugMessageCallback(nullptr, nullptr);
+        #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+        glDebugMessageCallbackKHR(nullptr, nullptr);
         #else
-        CORRADE_INTERNAL_ASSERT(false);
-        //glDebugMessageCallbackEXT(nullptr, nullptr);
+        CORRADE_ASSERT_UNREACHABLE();
         #endif
     }
 }
diff --git a/src/Magnum/Framebuffer.cpp b/src/Magnum/Framebuffer.cpp
index 3ae6ba369..840e1ad62 100644
--- a/src/Magnum/Framebuffer.cpp
+++ b/src/Magnum/Framebuffer.cpp
@@ -276,16 +276,16 @@ void Framebuffer::texture2DImplementationDSA(BufferAttachment attachment, GLenum
 #endif
 
 void Framebuffer::textureLayerImplementationDefault(BufferAttachment attachment, GLuint textureId, GLint mipLevel, GLint layer) {
-    /** @todo Re-enable when extension loader is available for ES 2.0 */
     #ifndef MAGNUM_TARGET_GLES2
     glFramebufferTextureLayer(GLenum(bindInternal()), GLenum(attachment), textureId, mipLevel, layer);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glFramebufferTexture3DOES(GLenum(bindInternal()), GLenum(attachment), GL_TEXTURE_3D_OES, textureId, mipLevel, layer);
     #else
     static_cast<void>(attachment);
     static_cast<void>(textureId);
     static_cast<void>(mipLevel);
     static_cast<void>(layer);
-    CORRADE_INTERNAL_ASSERT(false);
-    //glFramebufferTexture3DOES(GLenum(bindInternal()), GLenum(attachment), GL_TEXTURE_3D_OES, texture.id(), mipLevel, layer);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
diff --git a/src/Magnum/Mesh.cpp b/src/Magnum/Mesh.cpp
index 54ab76406..5028a0e45 100644
--- a/src/Magnum/Mesh.cpp
+++ b/src/Magnum/Mesh.cpp
@@ -285,14 +285,14 @@ void Mesh::drawInternal(Int count, Int baseVertex, Int instanceCount, GLintptr i
 }
 
 void Mesh::bindVAO(GLuint vao) {
-    /** @todo Re-enable when extension loader is available for ES */
     GLuint& current = Context::current()->state().mesh->currentVAO;
     if(current != vao) {
         #ifndef MAGNUM_TARGET_GLES2
         glBindVertexArray(current = vao);
+        #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+        glBindVertexArrayOES(current = vao);
         #else
-        CORRADE_INTERNAL_ASSERT(false);
-        //glBindVertexArrayOES(current = vao);
+        CORRADE_ASSERT_UNREACHABLE();
         #endif
     }
 }
@@ -300,12 +300,12 @@ void Mesh::bindVAO(GLuint vao) {
 void Mesh::createImplementationDefault() { _id = 0; }
 
 void Mesh::createImplementationVAO() {
-    /** @todo Get some extension wrangler instead to avoid linker errors to glGenVertexArrays() on ES2 */
     #ifndef MAGNUM_TARGET_GLES2
     glGenVertexArrays(1, &_id);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glGenVertexArraysOES(1, &_id);
     #else
-    //glGenVertexArraysOES(1, &_id);
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
     CORRADE_INTERNAL_ASSERT(_id != Implementation::State::DisengagedBinding);
 }
@@ -313,12 +313,12 @@ void Mesh::createImplementationVAO() {
 void Mesh::destroyImplementationDefault() {}
 
 void Mesh::destroyImplementationVAO() {
-    /** @todo Get some extension wrangler instead to avoid linker errors to glDeleteVertexArrays() on ES2 */
     #ifndef MAGNUM_TARGET_GLES2
     glDeleteVertexArrays(1, &_id);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDeleteVertexArraysOES(1, &_id);
     #else
-    //glDeleteVertexArraysOES(1, &_id);
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -426,24 +426,33 @@ void Mesh::vertexAttribPointer(const LongAttribute& attribute) {
 
 #ifdef MAGNUM_TARGET_GLES2
 void Mesh::vertexAttribDivisorImplementationANGLE(const GLuint index, const GLuint divisor) {
-    //glVertexAttribDivisorANGLE(index, divisor);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glVertexAttribDivisorANGLE(index, divisor);
+    #else
     static_cast<void>(index);
     static_cast<void>(divisor);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
 void Mesh::vertexAttribDivisorImplementationEXT(const GLuint index, const GLuint divisor) {
-    //glVertexAttribDivisorEXT(index, divisor);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glVertexAttribDivisorEXT(index, divisor);
+    #else
     static_cast<void>(index);
     static_cast<void>(divisor);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
 void Mesh::vertexAttribDivisorImplementationNV(const GLuint index, const GLuint divisor) {
-    //glVertexAttribDivisorNV(index, divisor);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glVertexAttribDivisorNV(index, divisor);
+    #else
     static_cast<void>(index);
     static_cast<void>(divisor);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 #endif
 
@@ -501,51 +510,69 @@ void Mesh::unbindImplementationVAO() {}
 
 #ifdef MAGNUM_TARGET_GLES2
 void Mesh::drawArraysInstancedImplementationANGLE(const GLint baseVertex, const GLsizei count, const GLsizei instanceCount) {
-    //glDrawArraysInstancedANGLE(GLenum(_primitive), baseVertex, count, instanceCount);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawArraysInstancedANGLE(GLenum(_primitive), baseVertex, count, instanceCount);
+    #else
     static_cast<void>(baseVertex);
     static_cast<void>(count);
     static_cast<void>(instanceCount);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
 void Mesh::drawArraysInstancedImplementationEXT(const GLint baseVertex, const GLsizei count, const GLsizei instanceCount) {
-    //glDrawArraysInstancedEXT(GLenum(_primitive), baseVertex, count, instanceCount);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawArraysInstancedEXT(GLenum(_primitive), baseVertex, count, instanceCount);
+    #else
     static_cast<void>(baseVertex);
     static_cast<void>(count);
     static_cast<void>(instanceCount);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
 void Mesh::drawArraysInstancedImplementationNV(const GLint baseVertex, const GLsizei count, const GLsizei instanceCount) {
-    //glDrawArraysInstancedNV(GLenum(_primitive), baseVertex, count, instanceCount);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawArraysInstancedNV(GLenum(_primitive), baseVertex, count, instanceCount);
+    #else
     static_cast<void>(baseVertex);
     static_cast<void>(count);
     static_cast<void>(instanceCount);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
 void Mesh::drawElementsInstancedImplementationANGLE(const GLsizei count, const GLintptr indexOffset, const GLsizei instanceCount) {
-    //glDrawElementsInstancedANGLE(GLenum(_primitive), count, GLenum(_indexType), reinterpret_cast<GLvoid*>(indexOffset), instanceCount);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawElementsInstancedANGLE(GLenum(_primitive), count, GLenum(_indexType), reinterpret_cast<GLvoid*>(indexOffset), instanceCount);
+    #else
     static_cast<void>(count);
     static_cast<void>(indexOffset);
     static_cast<void>(instanceCount);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
 void Mesh::drawElementsInstancedImplementationEXT(const GLsizei count, const GLintptr indexOffset, const GLsizei instanceCount) {
-    //glDrawElementsInstancedEXT(GLenum(_primitive), count, GLenum(_indexType), reinterpret_cast<GLvoid*>(indexOffset), instanceCount);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawElementsInstancedEXT(GLenum(_primitive), count, GLenum(_indexType), reinterpret_cast<GLvoid*>(indexOffset), instanceCount);
+    #else
     static_cast<void>(count);
     static_cast<void>(indexOffset);
     static_cast<void>(instanceCount);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
 void Mesh::drawElementsInstancedImplementationNV(const GLsizei count, const GLintptr indexOffset, const GLsizei instanceCount) {
-    //glDrawElementsInstancedNV(GLenum(_primitive), count, GLenum(_indexType), reinterpret_cast<GLvoid*>(indexOffset), instanceCount);
-    CORRADE_INTERNAL_ASSERT(false);
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glDrawElementsInstancedNV(GLenum(_primitive), count, GLenum(_indexType), reinterpret_cast<GLvoid*>(indexOffset), instanceCount);
+    #else
     static_cast<void>(count);
     static_cast<void>(indexOffset);
     static_cast<void>(instanceCount);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 #endif
 
diff --git a/src/Magnum/MeshView.cpp b/src/Magnum/MeshView.cpp
index bc5274030..165edd4a3 100644
--- a/src/Magnum/MeshView.cpp
+++ b/src/Magnum/MeshView.cpp
@@ -94,9 +94,10 @@ void MeshView::multiDrawImplementationDefault(std::initializer_list<std::referen
     if(!original._indexBuffer) {
         #ifndef MAGNUM_TARGET_GLES
         glMultiDrawArrays(GLenum(original._primitive), baseVertex, count, meshes.size());
+        #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+        glMultiDrawArraysEXT(GLenum(original._primitive), baseVertex, count, meshes.size());
         #else
-        //glMultiDrawArraysEXT(GLenum(original._primitive), baseVertex, count, meshes.size());
-        CORRADE_INTERNAL_ASSERT(false);
+        CORRADE_ASSERT_UNREACHABLE();
         #endif
 
     /* Indexed meshes */
@@ -112,9 +113,10 @@ void MeshView::multiDrawImplementationDefault(std::initializer_list<std::referen
         {
             #ifndef MAGNUM_TARGET_GLES
             glMultiDrawElements(GLenum(original._primitive), count, GLenum(original._indexType), indices, meshes.size());
+            #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+            glMultiDrawElementsEXT(GLenum(original._primitive), count, GLenum(original._indexType), indices, meshes.size());
             #else
-            //glMultiDrawElements(GLenum(original._primitive), count, GLenum(original._indexType), indices, meshes.size());
-            CORRADE_INTERNAL_ASSERT(false);
+            CORRADE_ASSERT_UNREACHABLE();
             #endif
         }
     }
diff --git a/src/Magnum/Query.cpp b/src/Magnum/Query.cpp
index 8fd4e7a15..3e01d4b8e 100644
--- a/src/Magnum/Query.cpp
+++ b/src/Magnum/Query.cpp
@@ -34,13 +34,12 @@
 namespace Magnum {
 
 AbstractQuery::AbstractQuery(): target() {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glGenQueries(1, &_id);
-    #elif defined(CORRADE_TARGET_NACL)
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN)
     glGenQueriesEXT(1, &_id);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -48,13 +47,12 @@ AbstractQuery::~AbstractQuery() {
     /* Moved out, nothing to do */
     if(!_id) return;
 
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glDeleteQueries(1, &_id);
-    #elif defined(CORRADE_TARGET_NACL)
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN)
     glDeleteQueriesEXT(1, &_id);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
@@ -78,14 +76,13 @@ AbstractQuery& AbstractQuery::setLabelInternal(const Containers::ArrayReference<
 bool AbstractQuery::resultAvailable() {
     CORRADE_ASSERT(!target, "AbstractQuery::resultAvailable(): the query is currently running", false);
 
-    /** @todo Re-enable when extension loader is available for ES */
     GLuint result;
     #ifndef MAGNUM_TARGET_GLES2
     glGetQueryObjectuiv(_id, GL_QUERY_RESULT_AVAILABLE, &result);
-    #elif defined(CORRADE_TARGET_NACL)
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN)
     glGetQueryObjectuivEXT(_id, GL_QUERY_RESULT_AVAILABLE_EXT, &result);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
     return result == GL_TRUE;
 }
@@ -94,14 +91,13 @@ bool AbstractQuery::resultAvailable() {
 template<> UnsignedInt AbstractQuery::result<UnsignedInt>() {
     CORRADE_ASSERT(!target, "AbstractQuery::result(): the query is currently running", {});
 
-    /** @todo Re-enable when extension loader is available for ES */
     UnsignedInt result;
     #ifndef MAGNUM_TARGET_GLES2
     glGetQueryObjectuiv(_id, GL_QUERY_RESULT, &result);
-    #elif defined(CORRADE_TARGET_NACL)
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN)
     glGetQueryObjectuivEXT(_id, GL_QUERY_RESULT_EXT, &result);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
     return result;
 }
@@ -111,14 +107,13 @@ template<> bool AbstractQuery::result<bool>() { return result<UnsignedInt>() !=
 template<> Int AbstractQuery::result<Int>() {
     CORRADE_ASSERT(!target, "AbstractQuery::result(): the query is currently running", {});
 
-    /** @todo Re-enable when extension loader is available for ES */
     Int result;
     #ifndef MAGNUM_TARGET_GLES
     glGetQueryObjectiv(_id, GL_QUERY_RESULT, &result);
-    #elif defined(CORRADE_TARGET_NACL)
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN)
     glGetQueryObjectivEXT(_id, GL_QUERY_RESULT_EXT, &result);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
     return result;
 }
@@ -127,13 +122,13 @@ template<> Int AbstractQuery::result<Int>() {
 template<> UnsignedLong AbstractQuery::result<UnsignedLong>() {
     CORRADE_ASSERT(!target, "AbstractQuery::result(): the query is currently running", {});
 
-    /** @todo Re-enable when extension loader is available for ES */
     UnsignedLong result;
     #ifndef MAGNUM_TARGET_GLES
     glGetQueryObjectui64v(_id, GL_QUERY_RESULT, &result);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glGetQueryObjectui64vEXT(_id, GL_QUERY_RESULT_EXT, &result);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glGetQueryObjectui64vEXT(_id, GL_QUERY_RESULT, &result);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
     return result;
 }
@@ -141,13 +136,13 @@ template<> UnsignedLong AbstractQuery::result<UnsignedLong>() {
 template<> Long AbstractQuery::result<Long>() {
     CORRADE_ASSERT(!target, "AbstractQuery::result(): the query is currently running", {});
 
-    /** @todo Re-enable when extension loader is available for ES */
     Long result;
     #ifndef MAGNUM_TARGET_GLES
     glGetQueryObjecti64v(_id, GL_QUERY_RESULT, &result);
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    glGetQueryObjecti64vEXT(_id, GL_QUERY_RESULT_EXT, &result);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //glGetQueryObjecti64vEXT(_id, GL_QUERY_RESULT, &result);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
     return result;
 }
@@ -157,27 +152,25 @@ template<> Long AbstractQuery::result<Long>() {
 void AbstractQuery::begin(GLenum target) {
     CORRADE_ASSERT(!this->target, "AbstractQuery::begin(): the query is already running", );
 
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glBeginQuery(this->target = target, id());
-    #elif defined(CORRADE_TARGET_NACL)
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN)
     glBeginQueryEXT(this->target = target, id());
     #else
     static_cast<void>(target);
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }
 
 void AbstractQuery::end() {
     CORRADE_ASSERT(target, "AbstractQuery::end(): the query is not running", );
 
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glEndQuery(target);
-    #elif defined(CORRADE_TARGET_NACL)
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN)
     glEndQueryEXT(target);
     #else
-    CORRADE_INTERNAL_ASSERT(false);
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
     target = {};
 }
diff --git a/src/Magnum/Query.h b/src/Magnum/Query.h
index 43242babf..50b917fdc 100644
--- a/src/Magnum/Query.h
+++ b/src/Magnum/Query.h
@@ -447,12 +447,12 @@ class TimeQuery: public AbstractQuery {
          * @see @fn_gl{QueryCounter} with @def_gl{TIMESTAMP}
          */
         void timestamp() {
-            /** @todo Enable when extension wrangler for ES is available */
             #ifndef MAGNUM_TARGET_GLES
             glQueryCounter(id(), GL_TIMESTAMP);
+            #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+            glQueryCounterEXT(id(), GL_TIMESTAMP_EXT);
             #else
-            //glQueryCounterEXT(id(), GL_TIMESTAMP);
-            CORRADE_INTERNAL_ASSERT(false);
+            CORRADE_ASSERT_UNREACHABLE();
             #endif
         }
 
diff --git a/src/Magnum/Renderbuffer.cpp b/src/Magnum/Renderbuffer.cpp
index 120795ab6..ef5a978cb 100644
--- a/src/Magnum/Renderbuffer.cpp
+++ b/src/Magnum/Renderbuffer.cpp
@@ -114,24 +114,34 @@ void Renderbuffer::storageImplementationDSA(RenderbufferFormat internalFormat, c
 }
 #endif
 
-/** @todo Re-enable when extension loader is available for ES */
-
 #ifndef MAGNUM_TARGET_GLES2
 void Renderbuffer::storageMultisampleImplementationDefault(const GLsizei samples, const RenderbufferFormat internalFormat, const Vector2i& size) {
     bind();
     glRenderbufferStorageMultisample(GL_RENDERBUFFER, samples, GLenum(internalFormat), size.x(), size.y());
 }
 #else
-void Renderbuffer::storageMultisampleImplementationANGLE(GLsizei, RenderbufferFormat, const Vector2i&) {
-    CORRADE_INTERNAL_ASSERT(false);
+void Renderbuffer::storageMultisampleImplementationANGLE(const GLsizei samples, const RenderbufferFormat internalFormat, const Vector2i& size) {
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
     bind();
-    //glRenderbufferStorageMultisampleANGLE(GL_RENDERBUFFER, samples, internalFormat, size.x(), size.y());
+    glRenderbufferStorageMultisampleANGLE(GL_RENDERBUFFER, samples, GLenum(internalFormat), size.x(), size.y());
+    #else
+    static_cast<void>(samples);
+    static_cast<void>(internalFormat);
+    static_cast<void>(size);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 
-void Renderbuffer::storageMultisampleImplementationNV(GLsizei, RenderbufferFormat, const Vector2i&) {
-    CORRADE_INTERNAL_ASSERT(false);
+void Renderbuffer::storageMultisampleImplementationNV(const GLsizei samples, const RenderbufferFormat internalFormat, const Vector2i& size) {
+    #if !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
     bind();
-    //glRenderbufferStorageMultisampleNV(GL_RENDERBUFFER, samples, internalFormat, size.x(), size.y());
+    glRenderbufferStorageMultisampleNV(GL_RENDERBUFFER, samples, GLenum(internalFormat), size.x(), size.y());
+    #else
+    static_cast<void>(samples);
+    static_cast<void>(internalFormat);
+    static_cast<void>(size);
+    CORRADE_ASSERT_UNREACHABLE();
+    #endif
 }
 #endif
 
diff --git a/src/Magnum/Renderer.cpp b/src/Magnum/Renderer.cpp
index 9d68aab86..83d642589 100644
--- a/src/Magnum/Renderer.cpp
+++ b/src/Magnum/Renderer.cpp
@@ -212,12 +212,12 @@ Renderer::GraphicsResetStatus Renderer::graphicsResetStatusImplementationDefault
 }
 
 Renderer::GraphicsResetStatus Renderer::graphicsResetStatusImplementationRobustness() {
-    /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES
     return GraphicsResetStatus(glGetGraphicsResetStatusARB());
+    #elif !defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(CORRADE_TARGET_NACL)
+    return GraphicsResetStatus(glGetGraphicsResetStatusEXT());
     #else
-    CORRADE_INTERNAL_ASSERT(false);
-    //return GraphicsResetStatus(glGetGraphicsResetStatusEXT());
+    CORRADE_ASSERT_UNREACHABLE();
     #endif
 }