diff --git a/js/src/builtin/MapObject.cpp b/js/src/builtin/MapObject.cpp
index d26a0f24b58..cd9194150ed 100644
--- a/js/src/builtin/MapObject.cpp
+++ b/js/src/builtin/MapObject.cpp
@@ -849,9 +849,11 @@ HashableValue::mark(JSTracer *trc) const
 
 /*** MapIterator *********************************************************************************/
 
-class js::MapIteratorObject : public JSObject
+class MapIteratorObject : public JSObject
 {
   public:
+    static Class class_;
+
     enum { TargetSlot, KindSlot, RangeSlot, SlotCount };
     static const JSFunctionSpec methods[];
     static MapIteratorObject *create(JSContext *cx, HandleObject mapobj, ValueMap *data,
@@ -866,14 +868,7 @@ class js::MapIteratorObject : public JSObject
     static JSBool next(JSContext *cx, unsigned argc, Value *vp);
 };
 
-inline js::MapIteratorObject &
-JSObject::asMapIterator()
-{
-    JS_ASSERT(isMapIterator());
-    return *static_cast<js::MapIteratorObject *>(this);
-}
-
-Class js::MapIteratorClass = {
+Class MapIteratorObject::class_ = {
     "Map Iterator",
     JSCLASS_IMPLEMENTS_BARRIERS |
     JSCLASS_HAS_RESERVED_SLOTS(MapIteratorObject::SlotCount),
@@ -913,7 +908,7 @@ GlobalObject::initMapIteratorProto(JSContext *cx, Handle<GlobalObject *> global)
     if (!base)
         return false;
     Rooted<JSObject*> proto(cx,
-        NewObjectWithGivenProto(cx, &MapIteratorClass, base, global));
+        NewObjectWithGivenProto(cx, &MapIteratorObject::class_, base, global));
     if (!proto)
         return false;
     proto->setSlot(MapIteratorObject::RangeSlot, PrivateValue(NULL));
@@ -936,7 +931,7 @@ MapIteratorObject::create(JSContext *cx, HandleObject mapobj, ValueMap *data,
     if (!range)
         return NULL;
 
-    JSObject *iterobj = NewObjectWithGivenProto(cx, &MapIteratorClass, proto, global);
+    JSObject *iterobj = NewObjectWithGivenProto(cx, &class_, proto, global);
     if (!iterobj) {
         js_delete(range);
         return NULL;
@@ -950,19 +945,19 @@ MapIteratorObject::create(JSContext *cx, HandleObject mapobj, ValueMap *data,
 void
 MapIteratorObject::finalize(FreeOp *fop, JSObject *obj)
 {
-    fop->delete_(obj->asMapIterator().range());
+    fop->delete_(obj->as<MapIteratorObject>().range());
 }
 
 bool
 MapIteratorObject::is(const Value &v)
 {
-    return v.isObject() && v.toObject().hasClass(&MapIteratorClass);
+    return v.isObject() && v.toObject().hasClass(&class_);
 }
 
 bool
 MapIteratorObject::next_impl(JSContext *cx, CallArgs args)
 {
-    MapIteratorObject &thisobj = args.thisv().toObject().asMapIterator();
+    MapIteratorObject &thisobj = args.thisv().toObject().as<MapIteratorObject>();
     ValueMap::Range *range = thisobj.range();
     if (!range)
         return js_ThrowStopIteration(cx);
diff --git a/js/src/jsobj.h b/js/src/jsobj.h
index 71d1aa2aa3b..321cdcee7e8 100644
--- a/js/src/jsobj.h
+++ b/js/src/jsobj.h
@@ -212,7 +212,6 @@ extern Class ErrorClass;
 extern Class GeneratorClass;
 extern Class IntlClass;
 extern Class JSONClass;
-extern Class MapIteratorClass;
 extern Class MathClass;
 extern Class NumberClass;
 extern Class ObjectClass;
@@ -234,7 +233,6 @@ class DebugScopeObject;
 class DeclEnvObject;
 class GlobalObject;
 class MapObject;
-class MapIteratorObject;
 class NestedScopeObject;
 class NewObjectCache;
 class NormalArgumentsObject;
@@ -979,7 +977,6 @@ class JSObject : public js::ObjectImpl
     inline bool isFunction()         const { return hasClass(&js::FunctionClass); }
     inline bool isGenerator()        const { return hasClass(&js::GeneratorClass); }
     inline bool isGlobal()           const;
-    inline bool isMapIterator()      const { return hasClass(&js::MapIteratorClass); }
     inline bool isObject()           const { return hasClass(&js::ObjectClass); }
     inline bool isPrimitive()        const { return isNumber() || isString() || isBoolean(); }
     inline bool isPropertyIterator() const;
@@ -1021,7 +1018,6 @@ class JSObject : public js::ObjectImpl
     inline js::DebugScopeObject &asDebugScope();
     inline js::GlobalObject &asGlobal();
     inline js::MapObject &asMap();
-    inline js::MapIteratorObject &asMapIterator();
     inline js::NestedScopeObject &asNestedScope();
     inline js::NumberObject &asNumber();
     inline js::PropertyIteratorObject &asPropertyIterator();