HttpMediaTypeNotSupportedException on mockmvc post

I have a RestController and a function that accepts post requests

@RequestMapping(path = "/auth",method = RequestMethod.POST)
public void authenticate(@RequestBody AuthenticationRequest authenticationRequest, HttpServletResponse httpServletResponse) throws  IOException {
}

I try to issue a post request

mockMvc.perform(post("/auth")
                    .contentType(MediaType.APPLICATION_JSON)
                    .content("{ \"foo\": \"bar\", \"fruit\": \"apple\" }".getBytes()))
            .andDo(print());

I receive

Resolved Exception:
         Type = org.springframework.web.HttpMediaTypeNotSupportedException

Any workaround ideas?