Imap checkinterval and Mutt 1.3.12

[walton]

I just upgraded to Mutt 1.3.12 from 1.2.5.  When I started it up, Mutt
complained that it didn't like my imap_checkinterval line in my .muttrc.  I
dug around the changelog but couldn't find the answer to my question (maybe
I just missed it):  is Mutt now constantly polling my imap server?  Or has
Mutt removed the check interval from being a configurable option?

Thanks!
Bryan