AsyncWriter is null. Vaadin 7.1.11 with @Push on Tomcat/Apache-Proxy


I have a problem again with @Push and Tomcat 7.0.54 (tried Tomcat 8.0.9 too).
When I open the WebApp on Tomcat I have no problems, but I have an Apache Server as proxy configurated using:

ProxyPass /WebApp http://tomcat_url:8080/WebApp
ProxyPassReverse /WebApp http://tomcat_url:8080/WebApp

<Location “/WebApp”>
Order allow,deny
Allow from all

[/code]So I am opening the WebApp http://webserver/WebApp and I see the following Message in the catalina.out Log file:

SEVERE: IllegalStateException. AsyncWriter is null. WebSocket and org.atmosphere.client.TrackMessageSizeInterceptor won't work. The only possible solution I see now is to configure Tomcat to use Port 80 which I don’t like because there is some other stuff running on the apache.

Thank you for any help in advance.

Ok using Vaadin 7.2.3 AND Tomcat 8 it is working.