Is it possible to change the default VAADIN dir to different one?

I have a problem using the guice and embedded jetty. I have 3 completely independent web applications (wars). Every of these wars contains couple of Vaadin applications, which shares the same VAADIN dir. But when I’m loading the wars the guice filter handles the incoming requests in order in which the guice modules are installed. And every three wars are serving the /VAADIN/* dir, which is than always handled by servlet first in the list.
I have set for every war different WebAppContext in jetty, where every war has different contextPath, and all three WebAppContexts are in one ContextHandlerCollection set to one Server instance.

How can I go around this problem, or how can I change the default VAADIN dir to be different for every war?

thanx in advance