diff --git a/libs/openzap/mod_openzap/mod_openzap.c b/libs/openzap/mod_openzap/mod_openzap.c
index ceabd3c547..c595e086b1 100644
--- a/libs/openzap/mod_openzap/mod_openzap.c
+++ b/libs/openzap/mod_openzap/mod_openzap.c
@@ -1248,6 +1248,12 @@ static ZIO_SIGNAL_CB_FUNCTION(on_isdn_signal)
     case ZAP_SIGEVENT_UP:
 		{
 			if ((session = zap_channel_get_session(sigmsg->channel, 0))) {
+				zap_tone_type_t tt = ZAP_TONE_DTMF;
+				
+				if (zap_channel_command(sigmsg->channel, ZAP_COMMAND_ENABLE_DTMF_DETECT, &tt) != ZAP_SUCCESS) {
+					zap_log(ZAP_LOG_ERROR, "TONE ERROR\n");
+				}
+
 				channel = switch_core_session_get_channel(session);
 				switch_channel_mark_answered(channel);
 				switch_core_session_rwunlock(session);