java.io.IOException: For now upgrade responses must have a content length of zero.

final WebSocketContainer container = ContainerProvider.getWebSocketContainer();
final URI securedEndpointURL = new URI("ws://echo.websocket.org:80"); // hrm, I really have to specify a port here ?

container.connectToServer(new Endpoint() {
  @Override
  public void onOpen(Session session, EndpointConfig config) {
    System.out.println("Connected!!!!!");
  }
},
ClientEndpointConfig.Builder.create().build(), // for some reason I have to provide that default config; Not so w/ Tyrus 
securedEndpointURL);

Exception in thread "main" java.io.IOException: For now upgrade responses must have a content length of zero.
	at org.xnio.http.HttpUpgrade$HttpUpgradeState.handleUpgrade(HttpUpgrade.java:351)
	at org.xnio.http.HttpUpgrade$HttpUpgradeState.access$900(HttpUpgrade.java:112)
	at org.xnio.http.HttpUpgrade$HttpUpgradeState$UpgradeResultListener.handleEvent(HttpUpgrade.java:335)
	at org.xnio.http.HttpUpgrade$HttpUpgradeState$UpgradeResultListener.handleEvent(HttpUpgrade.java:281)
	at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92)
	at org.xnio.conduits.ReadReadyHandler$ChannelListenerHandler.readReady(ReadReadyHandler.java:66)
	at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:87)
	at org.xnio.nio.WorkerThread.run(WorkerThread.java:531)