vsftpd doesn't log

[Deja Vu]

No matter what I've tried, I couldn't get vsftp to log...

Below are my log-related lines from /etc/vsftpd/vsftpd.conf

xferlog_enable=YES
log_ftp_protocol=YES
xferlog_file=/var/log/vsftpd.log
dual_log_enable=YES

please let me know if you can see any problem with these lines...

Thanks,