diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index b80737f35947..b921ab1be940 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -906,53 +906,14 @@ AtomIsEventHandlerName(nsIAtom *aName)
 nsIScriptGlobalObject *
 nsJSContext::GetGlobalObject()
 {
-  AutoJSContext cx;
-  JS::Rooted<JSObject*> global(mContext, GetWindowProxy());
-  if (!global) {
+  // Note: this could probably be simplified somewhat more; see bug 974327
+  // comments 1 and 3.
+  if (!mWindowProxy) {
     return nullptr;
   }
 
-  if (mGlobalObjectRef)
-    return mGlobalObjectRef;
-
-#ifdef DEBUG
-  {
-    JSObject *inner = JS_ObjectToInnerObject(cx, global);
-
-    // If this assertion hits then it means that we have a window object as
-    // our global, but we never called CreateOuterObject.
-    NS_ASSERTION(inner == global, "Shouldn't be able to innerize here");
-  }
-#endif
-
-  const JSClass *c = JS_GetClass(global);
-
-  nsCOMPtr<nsIScriptGlobalObject> sgo;
-  if (IsDOMClass(c)) {
-    sgo = do_QueryInterface(UnwrapDOMObjectToISupports(global));
-  } else {
-    if ((~c->flags) & (JSCLASS_HAS_PRIVATE |
-                       JSCLASS_PRIVATE_IS_NSISUPPORTS)) {
-      return nullptr;
-    }
-
-    nsISupports *priv = static_cast<nsISupports*>(js::GetObjectPrivate(global));
-
-    nsCOMPtr<nsIXPConnectWrappedNative> wrapped_native =
-      do_QueryInterface(priv);
-    if (wrapped_native) {
-      // The global object is a XPConnect wrapped native, the native in
-      // the wrapper might be the nsIScriptGlobalObject
-
-      sgo = do_QueryWrappedNative(wrapped_native);
-    } else {
-      sgo = do_QueryInterface(priv);
-    }
-  }
-
-  // This'll return a pointer to something we're about to release, but
-  // that's ok, the JS object will hold it alive long enough.
-  return sgo;
+  MOZ_ASSERT(mGlobalObjectRef);
+  return mGlobalObjectRef;
 }
 
 JSContext*