Strange problem with turning WAL archiving on

Hello,

I've spent a couple of hours trying some WAL archiving functionality on PostgrSQL 9.1 (running on Mac OS X). I turned on all the needed options as specified in the documentation:

wal_level = archive
archive_mode = on
archive_command='test ! -f /Volumes/baza/%f && cp %p /Volumes/baza/%f'

I also tried different archive commands, just to see if this is the case, but every time I try starting a backup (as postgres user) I got the following error:

tester=# select pg_start_backup('h');
ERROR: WAL level not sufficient for making an online backup
HINT: wal_level must be set to "archive" or "hot_standby" at server start.

The postgresql.conf file has all the changes I mentioned above and it was of course rebooted after the changes. I cannot find anything online regarding this issue, seems a bit strange as all the configuration looks all right, but the error is still here.

Thanks in advance,
BK