[CalendarServer-users] Login with ß in username

Dear all, I got a user with a german last Name with the character "ß" in it. The user can't login with iCal. The error log shows a strange sign instead of "ß" When I try to login trough the webbrowser, it works fine and it also writes the right sign into the logs. Does somone know how to fix this? Is this a problem with ical or is this a calendarserver problem? Thanks Ulrich Fourier