SSPI auth and mixed case usernames

Hello

Postgresql 11.2 on Windows.

I have a user mapping i pg_hba.conf

sspi map=domain

In pg_ident.conf, I have the following:

domain        /^(([A-Z|a-z]{3}[A|a]?)|([Xx]\d{2}))@DOMAIN$    \1

This maps windows logonname til a postgres username. Hower, for reasons I cannot explain, sometimes the username comes
inall-lowercase, at other times it comes all-caps. This is dependant on the Windows host the client is connected to.  

I do not want to create both XXX and xxx as users on Postgres. I would prefer to translate alle usernames to lowercase
inthe map.  

Is that possible, and if so, how?

Regards Niels Jespersen