diff --git a/widget/android/GfxInfo.h b/widget/android/GfxInfo.h
index f64a04fdc9c484335d3bae1fd8de1ddadb941b45..c70313972901e97ffa3acb4badee3785bfd3f422 100644
--- a/widget/android/GfxInfo.h
+++ b/widget/android/GfxInfo.h
@@ -64,7 +64,7 @@ public:
   NS_DECL_NSIGFXINFODEBUG
 #endif
 
-  virtual uint32_t OperatingSystemVersion();
+  virtual uint32_t OperatingSystemVersion() MOZ_OVERRIDE;
 
   virtual void InitializeGLStrings(gl::GLContext* gl);
 
diff --git a/widget/gonk/GfxInfo.cpp b/widget/gonk/GfxInfo.cpp
index d45226f7fc7be12504e387e35b91b75069b19589..719f0aedd0b53234455f6108073c246b6d3b952e 100644
--- a/widget/gonk/GfxInfo.cpp
+++ b/widget/gonk/GfxInfo.cpp
@@ -153,7 +153,7 @@ GfxInfo::GetGfxDriverInfo()
   return *mDriverInfo;
 }
 
-uint32_t GfxInfo::OperatingSystemVersion() const
+uint32_t GfxInfo::OperatingSystemVersion()
 {
   return 0;
 }
diff --git a/widget/gonk/GfxInfo.h b/widget/gonk/GfxInfo.h
index f97e963033d0f63a44a934e0651d05165eac2e3e..a75c4581e69ea83058fb511767144b2c732d7310 100644
--- a/widget/gonk/GfxInfo.h
+++ b/widget/gonk/GfxInfo.h
@@ -44,7 +44,7 @@ public:
   using GfxInfoBase::GetFeatureSuggestedDriverVersion;
   using GfxInfoBase::GetWebGLParameter;
 
-  virtual uint32_t OperatingSystemVersion() const;
+  virtual uint32_t OperatingSystemVersion() MOZ_OVERRIDE;
 
 #ifdef DEBUG
   NS_DECL_NSIGFXINFODEBUG
diff --git a/widget/windows/GfxInfo.h b/widget/windows/GfxInfo.h
index acb8995e762dc492c6bba7bb0a66e398531b0940..62d764dab176e688b595530cc3962e0ff7a7aad7 100644
--- a/widget/windows/GfxInfo.h
+++ b/widget/windows/GfxInfo.h
@@ -45,7 +45,7 @@ public:
 
   virtual nsresult Init();
 
-  virtual uint32_t OperatingSystemVersion() const { return mWindowsVersion; }
+  virtual uint32_t OperatingSystemVersion() MOZ_OVERRIDE { return mWindowsVersion; }
 
 #ifdef DEBUG
   NS_DECL_ISUPPORTS_INHERITED
diff --git a/widget/xpwidgets/GfxInfoBase.h b/widget/xpwidgets/GfxInfoBase.h
index 42932449c83f7fa19152fdfe828f1f8c7bf3579c..b3c438e85c13abb717bd254387cb8d82378e7f90 100644
--- a/widget/xpwidgets/GfxInfoBase.h
+++ b/widget/xpwidgets/GfxInfoBase.h
@@ -19,6 +19,7 @@
 #include "nsIGfxInfoDebug.h"
 #include "mozilla/Mutex.h"
 #include "js/Value.h"
+#include "mozilla/Attributes.h"
 
 namespace mozilla {
 namespace widget {