Install wizard: chosen lang on first step is not serialized on tomcat reboot (second part of the wizard)

I am trying to make some viewlets of the Jahia installer. My browser default lang is in FR. On the first screen of the installation wizard, I switch to EN. Ok the EN lang is serilaized .... until JJahia reboot. The second part of the wizard fall back in FR. Quite bad I have to redo my whole screencast