diff --git a/js/src/gc/StoreBuffer.h b/js/src/gc/StoreBuffer.h
index b734b97082c..137f9d7b1f6 100644
--- a/js/src/gc/StoreBuffer.h
+++ b/js/src/gc/StoreBuffer.h
@@ -356,17 +356,18 @@ class StoreBuffer
     class CallbackRef : public BufferableRef
     {
       public:
-        typedef void (*MarkCallback)(JSTracer *trc, void *key);
+        typedef void (*MarkCallback)(JSTracer *trc, void *key, void *data);
 
-        CallbackRef(MarkCallback cb, void *k) : callback(cb), key(k) {}
+        CallbackRef(MarkCallback cb, void *k, void *d) : callback(cb), key(k), data(d) {}
 
         virtual void mark(JSTracer *trc) {
-            callback(trc, key);
+            callback(trc, key, data);
         }
 
       private:
         MarkCallback callback;
         void *key;
+        void *data;
     };
 
     MonoTypeBuffer<ValueEdge> bufferVal;
@@ -451,8 +452,9 @@ class StoreBuffer
     }
 
     /* Insert or update a callback entry. */
-    void putCallback(CallbackRef::MarkCallback callback, void *key) {
-        bufferGeneric.put(CallbackRef(callback, key));
+    void putCallback(CallbackRef::MarkCallback callback, Cell *key, void *data) {
+        if (!key->isTenured())
+            bufferGeneric.put(CallbackRef(callback, key, data));
     }
 
     /* Mark the source of all edges in the store buffer. */
diff --git a/js/src/jsfriendapi.cpp b/js/src/jsfriendapi.cpp
index 483b818eae9..11ee2d207c9 100644
--- a/js/src/jsfriendapi.cpp
+++ b/js/src/jsfriendapi.cpp
@@ -1121,8 +1121,18 @@ js::IsInRequest(JSContext *cx)
 
 #ifdef JSGC_GENERATIONAL
 JS_FRIEND_API(void)
-JS_StorePostBarrierCallback(JSContext* cx, void (*callback)(JSTracer *trc, void *key), void *key)
+JS_StoreObjectPostBarrierCallback(JSContext* cx,
+                                  void (*callback)(JSTracer *trc, void *key, void *data),
+                                  JSObject *key, void *data)
 {
-    cx->runtime()->gcStoreBuffer.putCallback(callback, key);
+    cx->runtime()->gcStoreBuffer.putCallback(callback, key, data);
+}
+
+extern JS_FRIEND_API(void)
+JS_StoreStringPostBarrierCallback(JSContext* cx,
+                                  void (*callback)(JSTracer *trc, void *key, void *data),
+                                  JSString *key, void *data)
+{
+    cx->runtime()->gcStoreBuffer.putCallback(callback, key, data);
 }
 #endif /* JSGC_GENERATIONAL */
diff --git a/js/src/jsfriendapi.h b/js/src/jsfriendapi.h
index be8613c9048..9339dd7ee21 100644
--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -1794,10 +1794,24 @@ js_ReportIsNotFunction(JSContext *cx, const JS::Value& v);
 
 #ifdef JSGC_GENERATIONAL
 extern JS_FRIEND_API(void)
-JS_StorePostBarrierCallback(JSContext* cx, void (*callback)(JSTracer *trc, void *key), void *key);
+JS_StoreObjectPostBarrierCallback(JSContext* cx,
+                                  void (*callback)(JSTracer *trc, void *key, void *data),
+                                  JSObject *key, void *data);
+
+extern JS_FRIEND_API(void)
+JS_StoreStringPostBarrierCallback(JSContext* cx,
+                                  void (*callback)(JSTracer *trc, void *key, void *data),
+                                  JSString *key, void *data);
 #else
 inline void
-JS_StorePostBarrierCallback(JSContext* cx, void (*callback)(JSTracer *trc, void *key), void *key) {}
+JS_StoreObjectPostBarrierCallback(JSContext* cx,
+                                  void (*callback)(JSTracer *trc, void *key, void *data),
+                                  JSObject *key, void *data) {}
+
+inline void
+JS_StoreStringPostBarrierCallback(JSContext* cx,
+                                  void (*callback)(JSTracer *trc, void *key, void *data),
+                                  JSString *key, void *data) {}
 #endif /* JSGC_GENERATIONAL */
 
 #endif /* jsfriendapi_h */
diff --git a/js/xpconnect/src/XPCMaps.h b/js/xpconnect/src/XPCMaps.h
index 2978af41966..1a8152658f4 100644
--- a/js/xpconnect/src/XPCMaps.h
+++ b/js/xpconnect/src/XPCMaps.h
@@ -54,7 +54,7 @@ public:
             return p->value;
         if (!mTable.add(p, obj, wrapper))
             return nullptr;
-        JS_StorePostBarrierCallback(cx, KeyMarkCallback, obj);
+        JS_StoreObjectPostBarrierCallback(cx, KeyMarkCallback, obj, this);
         return wrapper;
     }
 
@@ -87,12 +87,11 @@ private:
      * This function is called during minor GCs for each key in the HashMap that
      * has been moved.
      */
-    static void KeyMarkCallback(JSTracer *trc, void *k) {
+    static void KeyMarkCallback(JSTracer *trc, void *k, void *d) {
         JSObject *key = static_cast<JSObject*>(k);
+        JSObject2WrappedJSMap* self = static_cast<JSObject2WrappedJSMap*>(d);
         JSObject *prior = key;
         JS_CallObjectTracer(trc, &key, "XPCJSRuntime::mWrappedJSMap key");
-        XPCJSRuntime* rt = nsXPConnect::GetRuntimeInstance();
-        JSObject2WrappedJSMap* self = rt->GetWrappedJSMap();
         self->mTable.rekey(prior, key);
     }
 
@@ -650,7 +649,7 @@ public:
         if (!mTable.add(p, key, value))
             return nullptr;
         MOZ_ASSERT(xpc::GetObjectScope(key)->mWaiverWrapperMap == this);
-        JS_StorePostBarrierCallback(cx, KeyMarkCallback, key);
+        JS_StoreObjectPostBarrierCallback(cx, KeyMarkCallback, key, this);
         return value;
     }
 
@@ -697,11 +696,11 @@ private:
      * This function is called during minor GCs for each key in the HashMap that
      * has been moved.
      */
-    static void KeyMarkCallback(JSTracer *trc, void *k) {
+    static void KeyMarkCallback(JSTracer *trc, void *k, void *d) {
         JSObject *key = static_cast<JSObject*>(k);
+        JSObject2JSObjectMap *self = static_cast<JSObject2JSObjectMap *>(d);
         JSObject *prior = key;
         JS_CallObjectTracer(trc, &key, "XPCWrappedNativeScope::mWaiverWrapperMap key");
-        JSObject2JSObjectMap *self = xpc::GetObjectScope(key)->mWaiverWrapperMap;
         self->mTable.rekey(prior, key);
     }