diff --git a/content/canvas/src/WebGLContext.cpp b/content/canvas/src/WebGLContext.cpp
index b585c9ffd01..bf7895d0645 100644
--- a/content/canvas/src/WebGLContext.cpp
+++ b/content/canvas/src/WebGLContext.cpp
@@ -1193,22 +1193,33 @@ NS_IMPL_CYCLE_COLLECTING_ADDREF(WebGLContext)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(WebGLContext)
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(WebGLContext)
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(WebGLContext)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(WebGLContext)
   NS_IMPL_CYCLE_COLLECTION_UNLINK_NSCOMPTR(mCanvasElement)
   NS_IMPL_CYCLE_COLLECTION_UNLINK_NSTARRAY(mEnabledExtensions)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(WebGLContext)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_NSCOMPTR(mCanvasElement)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_NSTARRAY_OF_NSCOMPTR(mEnabledExtensions)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 DOMCI_DATA(WebGLRenderingContext, WebGLContext)
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(WebGLContext)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
   NS_INTERFACE_MAP_ENTRY(nsIDOMWebGLRenderingContext)
   NS_INTERFACE_MAP_ENTRY(nsICanvasRenderingContextInternal)
   NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
   NS_INTERFACE_MAP_ENTRY(nsITimerCallback)
+  // If the exact way we cast to nsISupports here ever changes, fix our
+  // PreCreate hook!
   NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMWebGLRenderingContext)
   NS_DOM_INTERFACE_MAP_ENTRY_CLASSINFO(WebGLRenderingContext)
 NS_INTERFACE_MAP_END
diff --git a/content/canvas/src/WebGLContext.h b/content/canvas/src/WebGLContext.h
index cdd8230f9b0..f0c22e9449a 100644
--- a/content/canvas/src/WebGLContext.h
+++ b/content/canvas/src/WebGLContext.h
@@ -523,7 +523,8 @@ class WebGLContext :
     public nsICanvasRenderingContextInternal,
     public nsSupportsWeakReference,
     public nsITimerCallback,
-    public WebGLRectangleObject
+    public WebGLRectangleObject,
+    public nsWrapperCache
 {
     friend class WebGLMemoryMultiReporterWrapper;
     friend class WebGLExtensionLoseContext;
@@ -536,7 +537,12 @@ public:
 
     NS_DECL_CYCLE_COLLECTING_ISUPPORTS
 
-    NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(WebGLContext, nsIDOMWebGLRenderingContext)
+    NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(WebGLContext,
+                                                           nsIDOMWebGLRenderingContext)
+
+    nsINode* GetParentObject() {
+        return HTMLCanvasElement();
+    }
 
     NS_DECL_NSIDOMWEBGLRENDERINGCONTEXT
 
diff --git a/dom/base/nsDOMClassInfo.cpp b/dom/base/nsDOMClassInfo.cpp
index 758e252012b..792f64329ba 100644
--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -10908,8 +10908,20 @@ WebGLExtensionSH::PreCreate(nsISupports *nativeObj, JSContext *cx,
 
   WebGLExtension *ext = static_cast<WebGLExtension*>(nativeObj);
   WebGLContext *webgl = ext->Context();
-  nsHTMLCanvasElement *canvas = webgl->HTMLCanvasElement();
-  nsINode *node = static_cast<nsINode*>(canvas);
+  nsINode *node = webgl->GetParentObject();
+
+  return WrapNativeParent(cx, globalObj, node, node, parentObj);
+}
+
+NS_IMETHODIMP
+nsWebGLViewportHandlerSH::PreCreate(nsISupports *nativeObj, JSContext *cx,
+                                    JSObject *globalObj, JSObject **parentObj)
+{
+  *parentObj = globalObj;
+
+  WebGLContext *webgl = static_cast<WebGLContext*>(
+    static_cast<nsIDOMWebGLRenderingContext*>(nativeObj));
+  nsINode *node = webgl->GetParentObject();
 
   return WrapNativeParent(cx, globalObj, node, node, parentObj);
 }
diff --git a/dom/base/nsDOMClassInfo.h b/dom/base/nsDOMClassInfo.h
index 0f06bd8cac9..19f6c0063fc 100644
--- a/dom/base/nsDOMClassInfo.h
+++ b/dom/base/nsDOMClassInfo.h
@@ -1612,6 +1612,9 @@ public:
     return rv;
   }
 
+  NS_IMETHOD PreCreate(nsISupports *nativeObj, JSContext *cx,
+                       JSObject *globalObj, JSObject **parentObj);
+
   static nsIClassInfo *doCreate(nsDOMClassInfoData* aData)
   {
     return new nsWebGLViewportHandlerSH(aData);