[pmwiki-users] authgroup does not work

[info at hassanein.ch]

Hi

I have created some user groups in Site.AuthUser.

If I put the following lines into a page, it is always true, meaning  
even if the user is not in my_group.

(:if authgroup @my_group:)
show this only if you are in my_group
(:ifend:)

What am I doing wrong here?
--
Any help is very much appreciated.
Mike