[RCU] poppassd not working

I'm using poppassd as driver to password plugin that was bundled on the roundcube source installer. However, it is not working. When I change password, it always says "Could not save new password".

I tried to run poppassd manually and it is working fine in terminal. I've check syslog and found the ff when I change password in roundcube

Feb 12 16:07:23 mail xinetd[1562]: START: poppassd pid=2349 from=127.0.0.1 Feb 12 16:07:23 mail xinetd[1562]: EXIT: poppassd status=1 pid=2349 duration=0(sec)

It seems it exit immediately after changing password. Could this be a poppassd issue or a bug on roundcube v.0.5. ?