org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [com.package.Response] and content type [application/octet-stream]

@RestService
    RestClient restClient;
...
    String json = "{"param":3}";
    restClient.getRestTemplate().getMessageConverters().add(new GsonHttpMessageConverter());
    Response res = restClient.send(json);

@Rest("http://my-url.com")

    public interface RestClient
    {
        @Post("/something/")
        Response send(String json);

        RestTemplate getRestTemplate();

        void setRestTemplate(RestTemplate restTemplate);
    }