diff --git a/js/src/json.cpp b/js/src/json.cpp
index 8762bf596f5..954acf34a54 100644
--- a/js/src/json.cpp
+++ b/js/src/json.cpp
@@ -904,8 +904,7 @@ js_InitJSONClass(JSContext *cx, JSObject *obj)
     if (!JSON)
         return NULL;
     if (!JS_DefineProperty(cx, obj, js_JSON_str, OBJECT_TO_JSVAL(JSON),
-                           JS_PropertyStub, JS_PropertyStub,
-                           JSPROP_READONLY | JSPROP_PERMANENT))
+                           JS_PropertyStub, JS_PropertyStub, 0))
         return NULL;
 
     if (!JS_DefineFunctions(cx, JSON, json_static_methods))