md5 password authentication does not work when db_user_namespace = on

Hi,
when I set db_user_namespace = on in postgresql.conf and my pg_hba.conf contains only the line:
local   samerole    all    password
users can be authenticated (I have created users as username@dbname). However, when I change pg_hba's METHOD to md5, it doesn't work anymore. I attach my postgresql.conf.

cheers,
Sava Chankov