Enabling Push causes session to expire immediately

I am using Vaadin 8.0.6 running using jetty and trying to use push a UI update to the client using the following code:

getUI().access(()->{ saveBtn.setCaption("evaS"); getUI().push(); }); However, when I add @Push to the launcher class and try and view the page A Session Expired message comes up.
From the javascript console I get the following Errors:

com.vaadin.client.communication.MessageHandler SEVERE: Response didn't contain a server id. Please verify that the server is up-to-date and that the response data has not been modified in transmission. com.vaadin.client.communication.MessageHandler WARNING: Ignored received message because application has already been stopped The server appears to be running without any problems and doesn’t display any exceptions.
Any help would be greatly appreciated. Thanks

we had the same problem, see https://vaadin.com/forum#!/thread/15523853
seems to be fixed with Vaadin 8.1.0 beta

Thank you for sharing your discovery! I really appreciate it.
This is probably a newbie question but forgive me.
Where do I find the 8.1.0 beta? I don’t see it on their maven page.

Thank you again

see https://vaadin.com/releases?version=prerelease/8.1/8.1.0/8.1.0.beta1