diff --git a/dom/base/nsDOMClassInfo.cpp b/dom/base/nsDOMClassInfo.cpp
index 34e6b82476..bcba7bb66d 100644
--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -189,14 +189,18 @@ static nsDOMClassInfoData sClassInfoData[] = {
   // Misc Core related classes
 
   // CSS classes
-  NS_DEFINE_CLASSINFO_DATA(CSSStyleRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
-  NS_DEFINE_CLASSINFO_DATA(CSSImportRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
-  NS_DEFINE_CLASSINFO_DATA(CSSMediaRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
-  NS_DEFINE_CLASSINFO_DATA(CSSNameSpaceRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+  NS_DEFINE_CLASSINFO_DATA(CSSStyleRule, nsCSSRuleSH,
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
+  NS_DEFINE_CLASSINFO_DATA(CSSImportRule, nsCSSRuleSH,
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
+  NS_DEFINE_CLASSINFO_DATA(CSSMediaRule, nsCSSRuleSH,
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
+  NS_DEFINE_CLASSINFO_DATA(CSSNameSpaceRule, nsCSSRuleSH,
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   // XUL classes
 #ifdef MOZ_XUL
@@ -221,13 +225,16 @@ static nsDOMClassInfoData sClassInfoData[] = {
 #endif
 
   NS_DEFINE_CLASSINFO_DATA(CSSMozDocumentRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CLASSINFO_DATA(CSSSupportsRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CLASSINFO_DATA(CSSFontFaceRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CHROME_ONLY_CLASSINFO_DATA(ContentFrameMessageManager,
                                        nsMessageManagerSH<nsEventTargetSH>,
@@ -246,18 +253,23 @@ static nsDOMClassInfoData sClassInfoData[] = {
 
 
   NS_DEFINE_CLASSINFO_DATA(CSSKeyframeRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
   NS_DEFINE_CLASSINFO_DATA(CSSKeyframesRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CLASSINFO_DATA(CSSCounterStyleRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CLASSINFO_DATA(CSSPageRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CLASSINFO_DATA(CSSFontFeatureValuesRule, nsDOMGenericSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS)
+                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
+                           nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CHROME_XBL_CLASSINFO_DATA(XULControlElement, nsDOMGenericSH,
                                       DOM_DEFAULT_SCRIPTABLE_FLAGS)
@@ -1982,6 +1994,39 @@ nsEventTargetSH::PreserveWrapper(nsISupports *aNative)
   target->PreserveWrapper(aNative);
 }
 
+// CSS rule helper
+NS_IMETHODIMP
+nsCSSRuleSH::PreCreate(nsISupports *nativeObj, JSContext *cx,
+                       JSObject *aGlobalObj, JSObject **parentObj)
+{
+  JS::Rooted<JSObject*> globalObj(cx, aGlobalObj);
+  nsCOMPtr<nsIDOMCSSRule> rule = do_QueryInterface(nativeObj);
+  if (!rule) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  css::Rule* cssRule = rule->GetCSSRule();
+  if (!cssRule) {
+    // A DOMCSSStyleRule whose actual underlying rule has gone away.  There
+    // isn't much a caller can do with this thing anyway, and only chrome code
+    // can get its hands on it to start with, so just wrap in the current
+    // global.
+    *parentObj = globalObj;
+    return NS_OK;
+  }
+  nsIDocument* doc = cssRule->GetDocument();
+  if (!doc) {
+    *parentObj = globalObj;
+    return NS_OK;
+  }
+
+  nsIGlobalObject* global = doc->GetScopeObject();
+  if (!global) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  *parentObj = global->GetGlobalJSObject();
+  return *parentObj ? NS_OK : NS_ERROR_FAILURE;
+}
+
 // nsIDOMEventListener::HandleEvent() 'this' converter helper
 
 NS_INTERFACE_MAP_BEGIN(nsEventListenerThisTranslator)
diff --git a/dom/base/nsDOMClassInfo.h b/dom/base/nsDOMClassInfo.h
index 48f4966f0f..0d70b040bc 100644
--- a/dom/base/nsDOMClassInfo.h
+++ b/dom/base/nsDOMClassInfo.h
@@ -172,6 +172,29 @@ public:
   }
 };
 
+
+// Makes sure that we always create our wrapper in the right global, so we won't
+// cache one from the wrong global.
+class nsCSSRuleSH : public nsDOMGenericSH
+{
+protected:
+  explicit nsCSSRuleSH(nsDOMClassInfoData* aData) : nsDOMGenericSH(aData)
+  {
+  }
+
+  virtual ~nsCSSRuleSH()
+  {
+  }
+public:
+  NS_IMETHOD PreCreate(nsISupports *nativeObj, JSContext *cx,
+                       JSObject *globalObj, JSObject **parentObj) override;
+
+  static nsIClassInfo *doCreate(nsDOMClassInfoData* aData)
+  {
+    return new nsCSSRuleSH(aData);
+  }
+};
+
 // A place to hang some static methods that we should really consider
 // moving to be nsGlobalWindow member methods.  See bug 1062418.
 class nsWindowSH