[Exim] aliases file (gentoo)

i've installed exim on gentoo linux system
and in /etc/exim.conf :
never_users = root

and in /etc/aliases:
root: saper

but it's not working as it should :(
i've found in /var/log/mail.log:

Jun 23 16:01:56 saper exim[2378]: 2003-06-23 16:01:56 H=localhost [127.0.0.1]
F=<chd-admin@???> tem porarily rejected RCPT <root@localhost>: failed to open
SYSTEM_ALIASES_FILE for linear search: No such file or directory

where is the mistake ? where the aliases file should be ?
(the same aliases file i have got in /etc/mail/)

SaPeR