Why does Neoload 6.2.2 omit the Sec-WebSocket-Extensions header in the websocket handshake request?

I'm trying to get a websocket connection when validating my user-path, but I get the Error Code: NL-WEBSOCKET-CHANNEL-ENGINE.
After checking the difference in requests (using Fiddler) between neoload and the browser used during recording, I see that the header Sec-WebSocket-Extensions that is defined in the recorded request is not send to the server by Neoload. Why is that? Could this be a bug in version 6.2.2?