FIRMessagingDelegate causes a segmentation error: 11

Question

I use Swift 2.3 if I add this extension:

extension AppDelegate : FIRMessagingDelegate {
// Receive data message on iOS 10 devices.
func applicationReceivedRemoteMessage(remoteMessage: FIRMessagingRemoteMessage) {
    print("%@", remoteMessage.appData)
}

}

Xcode error with:

Swift command failed due to signal: Segmentation Error

I tried to clean / rebuild the project, get the data and restart Xcode (8.0)