Setting contentType to application/json leads to session cookie not being sent

[frankbolviken]

I have something along this request:

return when(reqwest({
      url: 'the_url',
      method: 'post',
      type: 'json',
      contentType: 'application/json',
      crossOrigin: true,
      withCredentials: true,
      data: data
    }))

Session cookie is not sent, and I get an error on API because it interprets it as I'm not logged in.
Removing contentType leads to cookie being sent and api is happy, but I get unsupported media-type ofc because contentType is interpreted as "application/x-www-form-urlencoded".

What am I doing wrong?

[javaLuo]

I have the same problem
this is a BUG ?