--- a/js/src/vm/RegExpObject.cpp
+++ b/js/src/vm/RegExpObject.cpp
@@ -739,17 +739,17 @@ RegExpCompartment::sizeOfExcludingThis(m
 
 JSObject *
 js::CloneRegExpObject(JSContext *cx, JSObject *obj_, JSObject *proto_)
 {
     RegExpObjectBuilder builder(cx);
     Rooted<RegExpObject*> regex(cx, &obj_->as<RegExpObject>());
     Rooted<RegExpObject*> proto(cx, &proto_->as<RegExpObject>());
     JSObject *res = builder.clone(regex, proto);
-    JS_ASSERT(res->type() == regex->type());
+    JS_ASSERT_IF(res, res->type() == regex->type());
     return res;
 }
 
 bool
 js::ParseRegExpFlags(JSContext *cx, JSString *flagStr, RegExpFlag *flagsOut)
 {
     size_t n = flagStr->length();
     const jschar *s = flagStr->getChars(cx);