diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 9f6b5c70962f..75e09b1385ec 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -2048,8 +2048,9 @@ nsGlobalWindow::SetOuterObject(JSContext* aCx, JS::Handle<JSObject*> aOuterObjec
 {
   JSAutoCompartment ac(aCx, aOuterObject);
 
-  // Indicate the default compartment object associated with this cx.
-  js::SetDefaultObjectForContext(aCx, aOuterObject);
+  // Inform the nsJSContext, which is the canonical holder of the outer.
+  MOZ_ASSERT(IsOuterWindow());
+  mContext->SetWindowProxy(aOuterObject);
 
   // Set up the prototype for the outer object.
   JS::Rooted<JSObject*> inner(aCx, JS_GetParent(aOuterObject));
@@ -2445,11 +2446,7 @@ nsGlobalWindow::SetNewDocument(nsIDocument* aDocument,
         newInnerWindow->FastGetGlobalJSObject());
 #endif
 
-    // Now that we're connecting the outer global to the inner one,
-    // we must have transplanted it. The JS engine tries to maintain
-    // the global object's compartment as its default compartment,
-    // so update that now since it might have changed.
-    js::SetDefaultObjectForContext(cx, mJSObject);
+    MOZ_ASSERT(mContext->GetWindowProxy() == mJSObject);
 #ifdef DEBUG
     JS::Rooted<JSObject*> rootedJSObject(cx, mJSObject);
     JS::Rooted<JSObject*> proto1(cx), proto2(cx);
diff --git a/dom/base/nsIScriptContext.h b/dom/base/nsIScriptContext.h
index 5c72e4781526..2b7e0c53cbe4 100644
--- a/dom/base/nsIScriptContext.h
+++ b/dom/base/nsIScriptContext.h
@@ -27,8 +27,8 @@ class nsIDOMWindow;
 class nsIURI;
 
 #define NS_ISCRIPTCONTEXT_IID \
-{ 0x1d931a17, 0x453a, 0x47fb, \
-  { 0x94, 0x66, 0x2d, 0x3e, 0xd1, 0xef, 0x7a, 0xc5 } }
+{ 0x03c0874e, 0xcb49, 0x41c8, \
+  { 0xa3, 0x0b, 0xef, 0x3e, 0xc1, 0x88, 0xb1, 0x1f } }
 
 /* This MUST match JSVERSION_DEFAULT.  This version stuff if we don't
    know what language we have is a little silly... */
@@ -165,6 +165,12 @@ public:
    * Tell the context we're done reinitializing it.
    */
   virtual void DidInitializeContext() = 0;
+
+  /**
+   * Access the Window Proxy. The setter should only be called by nsGlobalWindow.
+   */
+  virtual void SetWindowProxy(JS::Handle<JSObject*> aWindowProxy) = 0;
+  virtual JSObject* GetWindowProxy() = 0;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIScriptContext, NS_ISCRIPTCONTEXT_IID)
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index e66aa0d16237..488ef3d96002 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -1137,7 +1137,7 @@ nsJSContext::GetGlobalObject()
 JSObject*
 nsJSContext::GetNativeGlobal()
 {
-    return js::DefaultObjectForContextOrNull(mContext);
+    return GetWindowProxy();
 }
 
 JSContext*
@@ -2581,6 +2581,18 @@ nsJSContext::ReportPendingException()
   }
 }
 
+void
+nsJSContext::SetWindowProxy(JS::Handle<JSObject*> aWindowProxy)
+{
+  js::SetDefaultObjectForContext(mContext, aWindowProxy);
+}
+
+JSObject*
+nsJSContext::GetWindowProxy()
+{
+  return xpc_UnmarkGrayObject(js::DefaultObjectForContextOrNull(mContext));
+}
+
 void
 nsJSContext::LikelyShortLivingObjectCreated()
 {
diff --git a/dom/base/nsJSEnvironment.h b/dom/base/nsJSEnvironment.h
index 8cc9971e9761..3c95b5f977c8 100644
--- a/dom/base/nsJSEnvironment.h
+++ b/dom/base/nsJSEnvironment.h
@@ -80,6 +80,9 @@ public:
   virtual void WillInitializeContext() MOZ_OVERRIDE;
   virtual void DidInitializeContext() MOZ_OVERRIDE;
 
+  virtual void SetWindowProxy(JS::Handle<JSObject*> aWindowProxy) MOZ_OVERRIDE;
+  virtual JSObject* GetWindowProxy() MOZ_OVERRIDE;
+
   static void LoadStart();
   static void LoadEnd();