protected function temporaryCredentialsProtocolHeader($uri)
    {
        $parameters = array_merge($this->baseProtocolParameters(), array(
            'oauth_callback' => $this->clientCredentials->getCallbackUri(),
        ));

        $parameters['oauth_signature'] = $this->signature->sign($uri, $parameters, 'POST');

        return $this->normalizeProtocolParameters($parameters);
    }