Fb.ui apprequest returning null response

Question

After sending an Facebook app request in FB.ui using Javascript SDK, the response returned in the callback function is 'null', if the user sends the request or not. I have tested with multiple Facebook accounts and receive the app requests, however.

    , sendRequest: function() {
  parent.FB.ui({method: 'apprequests',
    to: this.game.attributes.opponentFbId,
    title: 'My App',
    message: 'I sent you a challenge on My App',
  }, function (response) {
                console.log(response)
        });

According to http://fbdevwiki.com/wiki/FB.ui, method 'apprequests' should return an array of request_ids (via response.request_ids), or response.to .However 'response' returns null when I try to log it in console

I have tried something similar with method 'feed' in FB.ui and can read the response (and response.post_id), however not with 'apprequests'.