diff --git a/config.tests/unix/opengldesktop/opengldesktop.cpp b/config.tests/unix/opengldesktop/opengldesktop.cpp
index 13e30593645..7ca8764a09b 100644
--- a/config.tests/unix/opengldesktop/opengldesktop.cpp
+++ b/config.tests/unix/opengldesktop/opengldesktop.cpp
@@ -34,6 +34,7 @@
 #ifdef __APPLE__
 #include <OpenGL/gl.h>
 #else
+#define GL_GLEXT_PROTOTYPES
 #include <GL/gl.h>
 #endif
 
diff --git a/config.tests/unix/opengles2/opengles2.cpp b/config.tests/unix/opengles2/opengles2.cpp
index b3b9be6d492..81926f3ee41 100644
--- a/config.tests/unix/opengles2/opengles2.cpp
+++ b/config.tests/unix/opengles2/opengles2.cpp
@@ -34,6 +34,7 @@
 #ifdef BUILD_ON_MAC
   #include <OpenGLES/ES2/gl.h>
 #else
+  #define GL_GLEXT_PROTOTYPES
   #include <GLES2/gl2.h>
 #endif
 
diff --git a/config.tests/unix/opengles3/opengles3.cpp b/config.tests/unix/opengles3/opengles3.cpp
index 506ac8b19c1..80b23234653 100644
--- a/config.tests/unix/opengles3/opengles3.cpp
+++ b/config.tests/unix/opengles3/opengles3.cpp
@@ -34,6 +34,7 @@
 #ifdef BUILD_ON_MAC
   #include <OpenGLES/ES3/gl.h>
 #else
+  #define GL_GLEXT_PROTOTYPES
   #include <GLES3/gl3.h>
 #endif
 
diff --git a/src/gui/opengl/qopengl.h b/src/gui/opengl/qopengl.h
index a060949c17e..aa0e6394d38 100644
--- a/src/gui/opengl/qopengl.h
+++ b/src/gui/opengl/qopengl.h
@@ -89,6 +89,13 @@ typedef void* GLeglImageOES;
 // applications cannot target ES 3. Therefore QOpenGLFunctions and
 // friends do everything dynamically and never rely on these macros.
 
+// Some Khronos headers use the ext proto guard in the standard headers as well,
+// which is bad. Work it around, but avoid spilling over to the ext header.
+#  ifndef GL_GLEXT_PROTOTYPES
+#   define GL_GLEXT_PROTOTYPES
+#   define QGL_TEMP_GLEXT_PROTO
+#  endif
+
 #  if defined(QT_OPENGL_ES_3_1)
 #   include <GLES3/gl31.h>
 #  elif defined(QT_OPENGL_ES_3)
@@ -97,6 +104,11 @@ typedef void* GLeglImageOES;
 #   include <GLES2/gl2.h>
 #endif
 
+#  ifdef QGL_TEMP_GLEXT_PROTO
+#   undef GL_GLEXT_PROTOTYPES
+#   undef QGL_TEMP_GLEXT_PROTO
+# endif
+
 /*
    Some GLES2 implementations (like the one on Harmattan) are missing the
    typedef for GLchar. Work around it here by adding it. The Kkronos headers
@@ -117,7 +129,15 @@ typedef char GLchar;
 #  include <OpenGL/glext.h>
 # else
 #  define GL_GLEXT_LEGACY // Prevents GL/gl.h from #including system glext.h
-#  include <GL/gl.h>
+// Some Khronos headers use the ext proto guard in the standard headers as well,
+// which is bad. Work it around, but avoid spilling over to the ext header.
+#  ifndef GL_GLEXT_PROTOTYPES
+#   define GL_GLEXT_PROTOTYPES
+#   include <GL/gl.h>
+#   undef GL_GLEXT_PROTOTYPES
+#  else
+#   include <GL/gl.h>
+#  endif
 #  include <QtGui/qopenglext.h>
 # endif // Q_OS_MAC
 #endif // QT_OPENGL_ES_2