edit: Retagged as tomcat, since this is really a question about the Tomcat embedded inside JBoss 6, rather than JBoss itself

I have an extremely simple servlet, which works on Glassfish v3. It uses Servlet 3.0 Asynchronous Processing. Here's a simplified version (which doesn't do much):

@WebServlet(asyncSupported=true)
public class SimpleServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException, IOException {

        final AsyncContext ac = request.startAsync();
        ac.setTimeout(3000);
    }
}

On JBoss 6.0.0 (Milestone 2), I get the following Exception:

java.lang.IllegalStateException: The servlet or filters that are being used
          by this request do not support async operation
    at org.apache.catalina.connector.Request.startAsync(Request.java:3096)
    at org.apache.catalina.connector.Request.startAsync(Request.java:3090)
    at org.apache.catalina.connector.RequestFacade.startAsync(RequestFacade.java:990)
    at playcomet.SimpleServlet.doGet(SimpleServlet.java:18)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
    ...

Do I have to do anything special to enable Asynchronous Processing in JBoss 6? Or do I need an additional deployment descriptor? ...