Vaadin 8: communication problem

In Vaadin 7 we get the expected “Communication problem: Take note of unsaved data, and click here or press ESC to continue. Invalid status code 0 (server down?)”. Now that we migrated to vaadin 8 we don’t get this error anymore when the server goes down. We can still click around in the UI but of course nothing happens. What can we do to get this exception message also with Vaadin 8?

You should eventually see the same error also with Vaadin 8 unless you have overriden system messages to disable it.

Thanks for the reply!
We were still using the reindeer theme from vaadin7. Using the reindeer theme from the vaadin-compatibility-themes makes it work again.