dovecot - May 2014 - antispam plugin doesn't recognize spam folder

After a recent upgrade to dovecot 2.2.9 (caused by an ubuntu upgrade to 
14.04), the antispam plugin has stopped recognizing my spam folders as 
spam.  I see the plugin initializes properly, but when moving a message, 
the mailbox_is_spam() function always returns 0.

The version of dovecot-antispam that ships with ubuntu is 
2.0+20130822-2build1.  I also compiled the latest version in the git 
repository (last update 9/12/2013) and had the same results.  This 
worked fine prior to the upgrade, with dovecot version 2.0.19 and 
dovecot-antispam version 2.0+20120225-2.

Here are the logs from initialization:
May 18 07:48:45 lebeau imap: antispam: plugin initialising (2.0-7-gabdad24)
May 18 07:48:45 lebeau imap: antispam: verbose debug enabled
May 18 07:48:45 lebeau imap: antispam: "SPAM" is exact match spam
folder
May 18 07:48:45 lebeau imap: antispam: "Spam" is exact match spam
folder
May 18 07:48:45 lebeau imap: antispam: "Junk" is exact match spam
folder
May 18 07:48:45 lebeau imap: antispam: no unsure folders
May 18 07:48:45 lebeau imap: antispam: "trash" is exact match trash
folder
May 18 07:48:45 lebeau imap: antispam: "Trash" is exact match trash
folder
May 18 07:48:45 lebeau imap: antispam: "Deleted Items" is exact match 
trash folder
May 18 07:48:45 lebeau imap: antispam: "Deleted Messages" is exact
match
trash folder
May 18 07:48:45 lebeau imap: antispam: dspam binary set to /usr/bin/dspam
May 18 07:48:45 lebeau imap: antispam: dspam extra arg --user
May 18 07:48:45 lebeau imap: antispam: dspam extra arg thenut at bytemonkey.net
May 18 07:48:45 lebeau imap: antispam: signature header line is 
"X-DSPAM-Signature"

And then from the message move:
May 18 07:50:06 lebeau imap: antispam: mailbox_is_unsure(SPAM): 0
May 18 07:50:06 lebeau imap: antispam: mailbox_is_trash(INBOX): 0
May 18 07:50:06 lebeau imap: antispam: mailbox_is_trash(SPAM): 0
May 18 07:50:06 lebeau imap: antispam: mail copy: from trash: 0, to trash: 0
May 18 07:50:06 lebeau imap: antispam: mailbox_is_spam(INBOX): 0
May 18 07:50:06 lebeau imap: antispam: mailbox_is_spam(SPAM): 0
May 18 07:50:06 lebeau imap: antispam: mailbox_is_unsure(INBOX): 0
May 18 07:50:06 lebeau imap: antispam: mail copy: src spam: 0, dst spam: 
0, src unsure: 0

Clearly mailbox_is_spam(SPAM) should return 1.

The other folders I have designated as spam (Junk and Spam) produce the 
same results.

~Paul