Firefox javax.faces.ViewState issue

Firefox javax.faces.ViewState issue

i am using jsf 2.1 on tomcat 7
the page renders javax.faces.ViewState as expected, when hitting f5 the
server sends a new id for javax.faces.ViewState, which is correct. But
firefox keeps the old value in the hidden input:
<input type="hidden" value="2442695108697186454:-4079620282104128276"
id="javax.faces.ViewState" name="javax.faces.ViewState">
The result is that the old view-scoped bean is taken on ajax requests.
only when i hit strg+f5 firefox takes the new value from server. I think
i's a feature of firefox (i often see when reloading a page with a form
firefox keeps my inputs).
any ideas how to deal with that?