[Freeswitch-users] Comfort noise or silence rtp packets during recording

I tried asking in the freeswitch irc channel but got no response. I'm trying my luck here. I have recently received a packet capture from the sipx community that seems to indicate that when FreeSwitch is recording a voice mail message via our custom IVR, that it does not send either comfort noise or silence packets back to the caller. This results to the call getting dropped by the ITSP after 30 seconds because of RTP time out. Is there a configurable parameter to make the IVR send some voice activity back? Joegen