Gamecenter GKServerStatusCode 5008 error

Hello, we're currently seeing the following error on our game while testing GameCenter functionality on iOS 9.3.1:

{
    GKServerStatusCode = 5008;
    NSLocalizedDescription = "The requested operation could not be completed due to an error communicating with the server.";
    NSUnderlyingError = "Error Domain=GKServerErrorDomain Code=5008 \"status = 5008, missing required header key: x-gk-bundle-version\" UserInfo={GKServerStatusCode=5008, NSLocalizedFailureReason=status = 5008, missing required header key: x-gk-bundle-version}";
}

Since we're just using the authenticateHandler, not sure how we could fix it. Also, I can't seem to find anything about that error. Any help would be appreciated.

Thanks!