APOP No Longer Working after Upgrade to IMAPd 2.3.12p2

[Jorey Bump]

I upgraded Cyrus IMAPd from 2.3.11 to 2.3.12p2 last night, and a user is 
now reporting that he can no longer authenticate using APOP. He's 
getting this error from his client:

'The server error encountered was: The POP server "mail.example.net" 
doesn’t support X-APOP authentication. Please check your account 
settings and try again. '

I haven't changed anything in the configuration that was working fine 
under 2.3.11. Any ideas?