--- a/gfx/gl/GLContextGLX.h
+++ b/gfx/gl/GLContextGLX.h
@@ -11,17 +11,17 @@
 #include "GLXLibrary.h"
 
 namespace mozilla {
 namespace gl {
 
 class GLContextGLX : public GLContext
 {
 public:
-    MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(GLContextGLX)
+    MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(GLContextGLX, MOZ_OVERRIDE)
     static already_AddRefed<GLContextGLX>
     CreateGLContext(const SurfaceCaps& caps,
                     GLContextGLX* shareContext,
                     bool isOffscreen,
                     Display* display,
                     GLXDrawable drawable,
                     GLXFBConfig cfg,
                     bool deleteDrawable,

--- a/gfx/gl/GLContextWGL.h
+++ b/gfx/gl/GLContextWGL.h
@@ -11,17 +11,17 @@
 #include "WGLLibrary.h"
 
 namespace mozilla {
 namespace gl {
 
 class GLContextWGL : public GLContext
 {
 public:
-    MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(GLContextWGL)
+    MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(GLContextWGL, MOZ_OVERRIDE)
     // From Window: (possibly for offscreen!)
     GLContextWGL(const SurfaceCaps& caps,
                  GLContext* sharedContext,
                  bool isOffscreen,
                  HDC aDC,
                  HGLRC aContext,
                  HWND aWindow = nullptr);