user.isUserInGroup return false if User in Master and group in virtual

--> A user is store in Master Wiki
--> This user is present in Wiki group in a virtual wiki
--> Calling API user.isUserInGroup in virtual wiki like :

$user.isUserInGroup("XWiki.AFKLM_AccepteCharte")
or
$user.isUserInGroup("virtualwiki:XWiki.AFKLM_AccepteCharte")

always return 'false'.
Previously with release 2.0.3, 'true' was return.

Julien