%d ignored from auth-passwdfile.conf.ext configuration file

I try to configure dovecot with virtual users. I put my users file in folder /etc/dovecot/my_domain_name/users. My auth-passwdfile.conf.ext file looks like this: passdb { driver = passwd-file args = username_format=%n /etc/dovecot/%d/users }

When I try to log in, I get this: dovecot: auth: Error: passwd-file(test,some.ip.addr.here,<rQT+ziijGE1tpoAB>): stat(/etc/dovecot//users) failed: No such file or directory

As you can see, %d isn't interpreted. Why is this happening? Any hints?

Thanks, Mura Andrei