ErraiAutoServlet will now become the default servlet to configure. This servlet contains a mechanism for automatically detecting which application server you are running on and automatically choosing the most appropriate implementation. Remove the Guice-Servlet listeners from your web.xml and replace it with the following declaration: <servlet> <servlet-name>ErraiAutoServlet</servlet-name> <servlet-class>org.jboss.errai.bus.server.servlet.ErraiAutoServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet <servlet-mapping> <servlet-name>ErraiAutoServlet</servlet-name> <url-pattern>*.erraiBus</url-pattern> </servlet-mapping> ... this is all you need.