WebSocket Session misses the UserProperties

My application uses custom javax.websocket.server.ServerEndpointConfig to setup custom javax.websocket.server.ServerEndpointConfig.Configurator that collects some information from the HandshakeRequest in the session's UserProperties.
With WFLY-2844 some problems have been fixed.
But now I see that the UserProperties are not available (i.e. it is 'null') from Session#getUserProperties() in javax.websocket.Endpoint#onOpen(Session, EndpointConfig)