diff --git a/daemon/call.c b/daemon/call.c
index 76998dd7c..ffa7d858f 100644
--- a/daemon/call.c
+++ b/daemon/call.c
@@ -821,6 +821,7 @@ struct call_media *call_media_new(struct call *call) {
 	med = uid_slice_alloc0(med, &call->medias);
 	med->call = call;
 	codec_store_init(&med->codecs, med);
+	mutex_init(&med->dtmf_lock);
 	return med;
 }
 
@@ -3332,6 +3333,7 @@ void call_media_free(struct call_media **mdp) {
 	codec_handler_free(&md->t38_handler);
 	t38_gateway_put(&md->t38_gateway);
 	g_queue_clear_full(&md->sdp_attributes, free);
+	mutex_destroy(&md->dtmf_lock);
 	g_slice_free1(sizeof(*md), md);
 	*mdp = NULL;
 }
diff --git a/daemon/codec.c b/daemon/codec.c
index 1c2287d04..0a212a734 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -129,7 +129,6 @@ struct codec_ssrc_handler {
 	int bytes_per_packet;
 	unsigned long first_ts; // for output TS scaling
 	unsigned long last_ts; // to detect input lag and handle lost packets
-	unsigned long ts_in; // for DTMF dupe detection
 	struct timeval first_send;
 	unsigned long first_send_ts;
 	long output_skew;
@@ -1748,17 +1747,21 @@ static struct codec_handler *__input_handler(struct codec_handler *h, struct med
 static int packet_dtmf(struct codec_ssrc_handler *ch, struct codec_ssrc_handler *input_ch,
 		struct transcode_packet *packet, struct media_packet *mp)
 {
-	if (ch->ts_in != packet->ts) { // ignore already processed events
-		int ret = dtmf_event(mp, packet->payload, ch->encoder_format.clockrate);
-		if (G_UNLIKELY(ret == -1)) // error
-			return -1;
-		if (ret == 1) {
-			// END event
-			ch->ts_in = packet->ts;
-			input_ch->dtmf_start_ts = 0;
+	{
+		LOCK(&mp->media->dtmf_lock);
+
+		if (mp->media->dtmf_ts != packet->ts) { // ignore already processed events
+			int ret = dtmf_event(mp, packet->payload, ch->encoder_format.clockrate);
+			if (G_UNLIKELY(ret == -1)) // error
+				return -1;
+			if (ret == 1) {
+				// END event
+				mp->media->dtmf_ts = packet->ts;
+				input_ch->dtmf_start_ts = 0;
+			}
+			else
+				input_ch->dtmf_start_ts = packet->ts ? packet->ts : 1;
 		}
-		else
-			input_ch->dtmf_start_ts = packet->ts ? packet->ts : 1;
 	}
 
 	int ret = 0;
diff --git a/include/call.h b/include/call.h
index bcfc81a1b..ad4441372 100644
--- a/include/call.h
+++ b/include/call.h
@@ -382,6 +382,10 @@ struct call_media {
 	//struct codec_handler	*dtmf_injector;
 	struct t38_gateway	*t38_gateway;
 	struct codec_handler	*t38_handler;
+
+	mutex_t			dtmf_lock;
+	unsigned long		dtmf_ts; // TS of last processed end event
+
 #ifdef WITH_TRANSCODING
 	union {
 		struct {