postfix error associated with spam trap

I've set up a few domains with the new 'spamtrap' aliases, sent a few spam emails to spamtrap@ and have since noticed the following error message in logwatch:

Unrecognized warning: unable to create lock file /var/virtualmin-traps/spam/120361479223136.lock: Permission denied : 3 Time(s)

Status: 
Closed (fixed)