protected function fetch(Request $request, $catch = false)
    {
        $subRequest = clone $request;

        // send no head requests because we want content
        if ('HEAD' === $request->getMethod()) {
            $subRequest->setMethod('GET');
        }

        // avoid that the backend sends no content
        $subRequest->headers->remove('if_modified_since');
        $subRequest->headers->remove('if_none_match');

        $response = $this->forward($subRequest, $catch);

        if ($response->isCacheable()) {
            $this->store($request, $response);
        }

        return $response;
    }