is string.gmatch(), string.upper() 7-bit ascii only?

[Marc Balmer <marc@...>]

I am trying to manipulate text with umlauts.  string.upper() does not produce upper case version of umlauts like ä,ö,ü etc.

Also the %g pattern, when used in string.gmatch() does not match these umlauts.

Is there anything that can be done about it?  Or, am I making a stupid mistake?