Symfony2: Redirecting to last route and flash a message?

I'm having a small problem when trying to flash a message and redirect the user back to the previous page in Symfony 2.

I have a very simple CRUD. When new, or edit, i want to flash a message if something goes wrong in the respective create/update methods:

1. User --GET--> new
2. new --POST--> create (fails)
3. --REDIRECT--> new (with flash message)

I'm doing the following:

  $this->container->get('session')->setFlash('error', 'myerror');
  $referer = $this->getRequest()->headers->get('referer');   
  return new RedirectResponse($referer);

However, it's not redirecting to the correct referrer! Even though the value of referrer is correct (eg.: http://localhost/demo/2/edit/) It redirects to the index. Why?