case insensitive regex clause with some latin1 characters fails

Hi,

I'm not sure if this is a bug or if I'm doing something wrong. I have
a database encoded with ISO-8859-1, aka LATIN1. When I do something
like:

SELECT 'Ä' ~* 'ä';

it returns false. If i do:

SELECT 'A' ~* 'a';

I get true. According to specification, both should return true.
Anyone knows what the problem might be?

/Ragnar