maildirlock time unit?

What is the time unit maildirlock will accept?

I've tried 20s, 20 sec, 20 secs, 20 seconds, all results in: Fatal: Invalid timeout value: 20s

And if you don't specify time unit you just get: Panic: BUG: No IOs or timeouts set. Not waiting for infinity.

This is on 2.3.3. 2.2 worked fine without needing time unit specified.