Assigning Crowd users to a Stash project doesn't work

Setup:

• Stash with Crowd-authentication
• a Crowd user "jack" that is member of group "stash-users"
• a Crowd user "jill" that is not member of this group
• a Stash project "myproject" that grants "contributor" permission to both user "jill" and group "stash-users"
• a Stash repo "repo" that belonghs to "myproject"

Now, "jack" is able to push to "repo", but "jill" is not (authentication fails)...