[TYPO3-mvc] Assign user group to a user

[Sebastian g]

Hi,

I built an extension which extends fe_users twice and fe_groups. Now I want to create users (programmatically) and assign an existing user group to them. Unfortunately I don't get the fe_groups record I want to assign from the FrontedUserGroupRepository until I set the group's record type to the extended group. I just get the groups which are set to the extended record type.
Any ideas how can I get the "raw" fe_group records?
-- 
regards
Seb