Perl Error in Webmin 1.279

I just started getting the following error after updating Webmin to the development version 1.279. I am running Virtualmin 3.16. The error occurs upon creation of a new mailbox user:

Error - Perl execution failed

Usage: POSIX::strftime(fmt, sec, min, hour, mday, mon, year, wday = -1, yday = -1, isdst = -1) at /usr/libexec/webmin/mailboxes/ line 826.

The mailbox is set up successfully, however the custom quota I entered did not take effect. It used the default quota for the domain, and I modified it successfully after the account was created.

Closed (fixed)