Sonata Page Bundle : Site : Is Default problem

[t...@wicrew.com]

I create 2 sites: FR and EN.
For FR site, I set relative path to empty and checked the box Is Default.
For EN site, I set relative path to "/en".
When I access http://sonata-test.local this is working.
But when I access http://sonata-test.local/en is doesn't work(page does not exist).

Then I try to set Is Default to EN site and uncheck Is Default in FR site, this working for both http://sonata-test.local , http://sonata-test.local/en

But I want to set FR site as default like first screen-shot.
This problem occur when one site have relative path empty.
Anyone have solution?