Possible bug updating user information from LDAP - A charset issue?

Hi guys!

I’ve connected my RT installation via RT::Authen::ExternalAuth to my active directory server.
All now is working fine, but I found in the logs, that my user information is updated every time i log on to RT saying in the logs

[8682] [Sat Jun 21 11:19:10 2014] [debug]: UPDATED user markus.wildbolz: User markus.wildbolz: City changed from ‘G?ssendorf’ to ‘G?ssendorf’ (/opt/rt4/local/plugins/RT-Authen-ExternalAuth/lib/RT/Authen/ExternalAuth.pm:452)

But there is no change in the user information in AD. Maybe this has something todo with the used character set, because the right value would be ‘Gössendorf’ (or same issue with ‘Österreich’).

Is there any possibility to get rid of this??