[undertow-dev] Forwarding initial websocket request

I am trying to forward the initial websocket http request coming in via a Servlet filter with the forward method (I want to cut off the first path segment): final String requestUri = HttpServletRequest.class.cast(servletRequest).getRequestURI(); final String newRequestUri = requestUri.substring(requestUri.indexOf("/", 1)); servletRequest.getRequestDispatcher(newRequestUri).forward(servletRequest, servletResponse); The filter is triggered successfully, but the websocket is not initialized instead 404 is returned. Is this correct according to spec? How can I forward such requests? Thankx Lukas