--- a/js/xpconnect/src/XPCMaps.cpp
+++ b/js/xpconnect/src/XPCMaps.cpp
@@ -114,22 +114,21 @@ JSObject2WrappedJSMap::UpdateWeakPointer
                 if (!wrapper->GetJSObjectPreserveColor())
                     dying.AppendElement(dont_AddRef(wrapper));
             }
             wrapper = wrapper->GetNextWrapper();
         }
 
         // Remove or update the JSObject key in the table if necessary.
         JSObject* obj = e.front().key();
-        JSObject* prior = obj;
         JS_UpdateWeakPointerAfterGCUnbarriered(&obj);
         if (!obj)
             e.removeFront();
-        else if (obj != prior)
-            e.rekeyFront(obj);
+        else
+            e.front().mutableKey() = obj;
     }
 }
 
 void
 JSObject2WrappedJSMap::ShutdownMarker()
 {
     for (Map::Range r = mTable.all(); !r.empty(); r.popFront()) {
         nsXPCWrappedJS* wrapper = r.front().value();

--- a/js/xpconnect/src/XPCMaps.h
+++ b/js/xpconnect/src/XPCMaps.h
@@ -22,18 +22,20 @@
 
 // no virtuals in the maps - all the common stuff inlined
 // templates could be used to good effect here.
 
 /*************************/
 
 class JSObject2WrappedJSMap
 {
-    typedef js::HashMap<JSObject*, nsXPCWrappedJS*, js::PointerHasher<JSObject*, 3>,
-                        js::SystemAllocPolicy> Map;
+    using Map = js::HashMap<JS::Heap<JSObject*>,
+                            nsXPCWrappedJS*,
+                            js::MovableCellHasher<JS::Heap<JSObject*>>,
+                            js::SystemAllocPolicy>;
 
 public:
     static JSObject2WrappedJSMap* newMap(int length) {
         JSObject2WrappedJSMap* map = new JSObject2WrappedJSMap();
         if (!map->mTable.init(length)) {
             // This is a decent estimate of the size of the hash table's
             // entry storage. The |2| is because on average the capacity is
             // twice the requested length.
@@ -61,17 +63,16 @@ public:
     inline nsXPCWrappedJS* Add(JSContext* cx, nsXPCWrappedJS* wrapper) {
         NS_PRECONDITION(wrapper,"bad param");
         JSObject* obj = wrapper->GetJSObjectPreserveColor();
         Map::AddPtr p = mTable.lookupForAdd(obj);
         if (p)
             return p->value();
         if (!mTable.add(p, obj, wrapper))
             return nullptr;
-        JS_StoreObjectPostBarrierCallback(cx, KeyMarkCallback, obj, this);
         return wrapper;
     }
 
     inline void Remove(nsXPCWrappedJS* wrapper) {
         NS_PRECONDITION(wrapper,"bad param");
         mTable.remove(wrapper->GetJSObjectPreserveColor());
     }
 
@@ -90,27 +91,16 @@ public:
 
     // Report the sum of SizeOfIncludingThis() for all wrapped JS in the map.
     // Each wrapped JS is only in one map.
     size_t SizeOfWrappedJS(mozilla::MallocSizeOf mallocSizeOf) const;
 
 private:
     JSObject2WrappedJSMap() {}
 
-    /*
-     * This function is called during minor GCs for each key in the HashMap that
-     * has been moved.
-     */
-    static void KeyMarkCallback(JSTracer* trc, JSObject* key, void* data) {
-        JSObject2WrappedJSMap* self = static_cast<JSObject2WrappedJSMap*>(data);
-        JSObject* prior = key;
-        JS_CallUnbarrieredObjectTracer(trc, &key, "XPCJSRuntime::mWrappedJSMap key");
-        self->mTable.rekeyIfMoved(prior, key);
-    }
-
     Map mTable;
 };
 
 /*************************/
 
 class Native2WrappedNativeMap
 {
 public: