Vaadin 8 with Liferay on OSGI


I creating an portal with Vaadin 8 on Liferay 7.2.
The whole system works fine, but we needed to change our root directory to a different.
This create the error, that the resources links for bootstrap etc from Vaadin theme are not correct anymore:
Failed to load the bootstrap javascript: /o/vaadin-8.9.0/VAADIN/vaadinBootstrap.js?v=8.9.0
I don’t know where i can tell vaadin, that it needs to add a prefix to this link.

Someone has an idea, where Vaadin reads this property?