diff --git a/openbsc/src/libmgcp/mgcp_transcode.c b/openbsc/src/libmgcp/mgcp_transcode.c
index ff20fb8..8e14d7f 100644
--- a/openbsc/src/libmgcp/mgcp_transcode.c
+++ b/openbsc/src/libmgcp/mgcp_transcode.c
@@ -428,10 +428,12 @@
 
 	if (payload_len > 0) {
 		ts_no = ntohl(*(uint32_t*)(data+4));
-		if (!state->is_running)
+		if (!state->is_running) {
 			state->next_seq = ntohs(*(uint16_t*)(data+2));
+			state->next_time = ts_no;
+			state->is_running = 1;
+		}
 
-		state->is_running = 1;
 
 		if (state->sample_cnt > 0) {
 			int32_t delta = ts_no - state->next_time;
diff --git a/openbsc/tests/mgcp/mgcp_transcoding_test.c b/openbsc/tests/mgcp/mgcp_transcoding_test.c
index 27d7269..3974695 100644
--- a/openbsc/tests/mgcp/mgcp_transcoding_test.c
+++ b/openbsc/tests/mgcp/mgcp_transcoding_test.c
@@ -120,18 +120,18 @@
 		"\xD5\xA5\xA3\xA5\xD5\x25\x23\x25\xD5\xA5\xA3\xA5\xD5\x25\x23\x25"
 		"\xD5\xA5\xA3\xA5\xD5\x25\x23\x25\xD5\xA5\xA3\xA5\xD5\x25\x23\x25"
 	},
-	/* RTP: SeqNo=26527, TS=0 */
+	/* RTP: SeqNo=26527, TS=232640 */
 	{0.020000, 92,
-		"\x80\x08\x67\x9f\x00\x00\x00\x00\x04\xaa\x67\x9f\xd5\xd5\xd5\xd5"
+		"\x80\x08\x67\x9f\x00\x03\x8c\xc0\x04\xaa\x67\x9f\xd5\xd5\xd5\xd5"
 		"\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5"
 		"\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5"
 		"\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5\xd5"
 		"\xd5\xd5\xd5\xd5\xd5\xd5\x55\x55\xd5\xd5\x55\x55\xd5\xd5\x55\x55"
 		"\xd5\xd5\xd5\x55\x55\xd5\xd5\xd5\x55\x55\xd5\xd5"
 	},
-	/* RTP: SeqNo=26528, TS=80 */
+	/* RTP: SeqNo=26528, TS=232720 */
 	{0.020000, 92,
-		"\x80\x08\x67\xa0\x00\x00\x00\x50\x04\xaa\x67\x9f\x55\xd5\xd5\x55"
+		"\x80\x08\x67\xa0\x00\x03\x8d\x10\x04\xaa\x67\x9f\x55\xd5\xd5\x55"
 		"\xd5\x55\xd5\xd5\xd5\x55\xd5\x55\xd5\xd5\x55\xd5\x55\xd5\x55\xd5"
 		"\x55\x55\xd5\x55\xd5\xd5\x55\x55\x55\x55\x55\xd5\xd5\x55\xd5\xd5"
 		"\xd5\x55\xd5\xd5\xd5\x55\x54\x55\xd5\xd5\x55\xd5\xd5\xd5\xd5\x55"
@@ -352,6 +352,7 @@
 		memcpy(buf, audio_packets_pcma[1].data, len);
 		res = mgcp_transcoding_process_rtp(endp, &endp->bts_end, buf, &len, ARRAY_SIZE(buf));
 		OSMO_ASSERT(state->sample_cnt == 80);
+		OSMO_ASSERT(state->next_time == 232640);
 		OSMO_ASSERT(res < 0);
 
 		/* Add the second sample and it should be consumable */
@@ -359,6 +360,7 @@
 		memcpy(buf, audio_packets_pcma[2].data, len);
 		res = mgcp_transcoding_process_rtp(endp, &endp->bts_end, buf, &len, ARRAY_SIZE(buf));
 		OSMO_ASSERT(state->sample_cnt == 0);
+		OSMO_ASSERT(state->next_time == 232640 + 80 + 160);
 		OSMO_ASSERT(res == sizeof(struct rtp_hdr));
 
 		talloc_free(ctx);