chan_misdn in 1.2.20 does not recognize dtmf tones

Hi all

I have a Digium b410p. I just upgraded Asterisk from 1.2.19 to 1.2.20. After the upgrade, asterisk is not recognizing dtmf tones coming in from isdn.
If I downgrade Asterisk to 1.2.19, the problem disappears.
If I take the file from 1.2.20, and use it in 1.2.19, the problem reappears again. So it seems the problem is really there. What can it be? Should I file a bug?

FIY, I tried with mISDN 1.1.2 and 1.1.4, changing dtmf and dtmfthreshold options in /etc/mISDN.conf, but nothing changes.