Turn Based Matches: GKMatchRequest.RecipientResponse does not seem to work

When specifying a callback in GKMatchRequest.RecipientResponse and callling GKTurnBasedMatchmakerViewController.Request( request ) the response callback function never gets called, even if the invited player makes a turn or calls AcceptInvite()
Furthermore the callback function should get the MatchID as a parameter. Now it is not possible to know for which match the invitation was accepted (there might be several invitations pending!)