--- a/gfx/gl/GLContextProviderGLX.cpp
+++ b/gfx/gl/GLContextProviderGLX.cpp
@@ -10,16 +10,17 @@
 #elif defined(MOZ_WIDGET_QT)
 #define GET_NATIVE_WINDOW(aWidget) (Window)(aWidget->GetNativeData(NS_NATIVE_SHAREABLE_WINDOW))
 #endif
 
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 
 #include "mozilla/MathAlgorithms.h"
+#include "mozilla/StaticPtr.h"
 #include "mozilla/X11Util.h"
 
 #include "prenv.h"
 #include "GLContextProvider.h"
 #include "GLLibraryLoader.h"
 #include "nsDebug.h"
 #include "nsIWidget.h"
 #include "GLXLibrary.h"
@@ -1183,34 +1184,38 @@ GLContextProviderGLX::CreateOffscreen(co
         return nullptr;
 
     if (!glContext->InitOffscreen(ToIntSize(size), caps))
         return nullptr;
 
     return glContext.forget();
 }
 
-static nsRefPtr<GLContext> gGlobalContext;
+static StaticRefPtr<GLContext> gGlobalContext;
 // TODO move that out of static initializaion
 static bool gUseContextSharing = getenv("MOZ_DISABLE_CONTEXT_SHARING_GLX") == 0;
 
 GLContext*
 GLContextProviderGLX::GetGlobalContext()
 {
     // TODO: get GLX context sharing to work well with multiple threads
     if (!gUseContextSharing) {
         return nullptr;
     }
 
     static bool triedToCreateContext = false;
     if (!triedToCreateContext && !gGlobalContext) {
         triedToCreateContext = true;
 
         gfxIntSize dummySize = gfxIntSize(16, 16);
-        gGlobalContext = CreateOffscreenPixmapContext(dummySize);
+        // StaticPtr doesn't support assignments from already_AddRefed,
+        // so use a temporary nsRefPtr to make the reference counting
+        // fall out correctly.
+        nsRefPtr<GLContext> holder = CreateOffscreenPixmapContext(dummySize);
+        gGlobalContext = holder;
     }
 
     return gGlobalContext;
 }
 
 void
 GLContextProviderGLX::Shutdown()
 {