- _, rw, jresp = s.doRequest(c, token, "POST", `/arvados/v1/collections`, nil, bytes.NewBufferString(`ensure_unique_name=true`))
+ _, rw, jresp = s.doRequest(c, token, "POST", `/arvados/v1/collections`, http.Header{"Content-Type": {"application/x-www-form-urlencoded"}}, bytes.NewBufferString(`ensure_unique_name=true`))