--- a/js/src/xpconnect/src/xpcjsid.cpp
+++ b/js/src/xpconnect/src/xpcjsid.cpp
@@ -889,17 +889,17 @@ nsJSCID::HasInstance(nsIXPConnectWrapped
 
         NS_ASSERTION(obj, "when is an object not an object?");
 
         // is this really a native xpcom object with a wrapper?
         JSObject* obj2;
         XPCWrappedNative* other_wrapper =
            XPCWrappedNative::GetWrappedNativeOfJSObject(cx, obj, nsnull, &obj2);
 
-        if(!other_wrapper || !obj2)
+        if(!other_wrapper && !obj2)
             return NS_OK;
 
         nsIClassInfo* ci = other_wrapper ?
                            other_wrapper->GetClassInfo() :
                            GetSlimWrapperProto(obj2)->GetClassInfo();
 
         // We consider CID equality to be the thing that matters here.
         // This is perhaps debatable.