diff --git a/daemon/codec.c b/daemon/codec.c
index 4bd817674..580fd473e 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -3393,7 +3393,8 @@ static bool __buffer_dtx(struct dtx_buffer *dtxb, struct codec_ssrc_handler *dec
 
 	unsigned long ts = packet ? packet->ts : 0;
 
-	if (!mp->ssrc_out->seq_set) {
+	// Discard entries have no packet; initialize sequencing with the first real packet.
+	if (packet && !mp->ssrc_out->seq_set) {
 		mp->ssrc_out->seq_set = true;
 		mp->ssrc_out->seq_out = packet->p.seq;
 	}
diff --git a/t/Makefile b/t/Makefile
index d70fb778c..e7b76ad99 100644
--- a/t/Makefile
+++ b/t/Makefile
@@ -109,7 +109,8 @@ include ../lib/common.Makefile
 	daemon-tests-templ-def daemon-tests-templ-def-offer daemon-tests-t38 daemon-tests-evs-dtx \
 	daemon-tests-transform daemon-tests-http daemon-tests-heuristic daemon-tests-asymmetric \
 	daemon-tests-dtx-no-shift daemon-tests-rtcp daemon-tests-redis-subscribe \
-	daemon-tests-recording
+	daemon-tests-recording \
+	daemon-tests-dtx-dtmf
 
 TESTS=		test-bitstr aes-crypt aead-aes-crypt test-const_str_hash.strhash
 ifeq ($(with_transcoding),yes)
@@ -157,7 +158,8 @@ daemon-tests: daemon-tests-main daemon-tests-jb daemon-tests-pubsub daemon-tests
 	daemon-tests-sdp-orig-replacements daemon-tests-moh daemon-tests-evs-dtx daemon-tests-transform \
 	daemon-tests-transcode-config daemon-tests-codec-prefs daemon-tests-http daemon-tests-heuristic \
 	daemon-tests-asymmetric daemon-tests-rtcp daemon-tests-redis-subscribe \
-	daemon-tests-recording
+	daemon-tests-recording \
+	daemon-tests-dtx-dtmf
 
 daemon-test-deps:	tests-preload.so
 	$(MAKE) -C ../daemon
@@ -177,6 +179,9 @@ daemon-tests-asymmetric:	daemon-test-deps
 daemon-tests-dtx:	daemon-test-deps
 	./auto-test-helper "$@" perl -I../perl auto-daemon-tests-dtx.pl
 
+daemon-tests-dtx-dtmf:	daemon-test-deps
+	./auto-test-helper "$@" perl -I../perl auto-daemon-tests-dtx-dtmf.pl
+
 daemon-tests-dtx-no-shift:	daemon-test-deps
 	./auto-test-helper "$@" perl -I../perl auto-daemon-tests-dtx-no-shift.pl
 
diff --git a/t/auto-daemon-tests-dtx-dtmf.pl b/t/auto-daemon-tests-dtx-dtmf.pl
new file mode 100755
index 000000000..bba2094cb
--- /dev/null
+++ b/t/auto-daemon-tests-dtx-dtmf.pl
@@ -0,0 +1,87 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use NGCP::Rtpengine::Test;
+use NGCP::Rtpclient::SRTP;
+use NGCP::Rtpengine::AutoTest;
+use Test::More;
+
+# Run without extended codec dependencies: G.711 also supports DTX buffering.
+autotest_start(qw(--config-file=none -t -1 -i 203.0.113.1
+	-n 2223 -f -L 7 -E --silence-detect=1 --dtx-delay=50)) or die;
+
+my ($sock_a, $sock_b) = new_call([qw(198.51.100.10 5000)], [qw(198.51.100.10 5002)]);
+my $name = 'DTMF suppression before first DTX audio packet';
+
+my ($port_a) = offer($name, { codec => { transcode => ['PCMA'] } }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.10
+s=tester
+t=0 0
+m=audio 5000 RTP/AVP 0 101
+c=IN IP4 198.51.100.10
+a=rtpmap:101 telephone-event/8000
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.10
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 0 8 101
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=rtpmap:8 PCMA/8000
+a=rtpmap:101 telephone-event/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+my ($port_b) = answer($name, {}, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.10
+s=tester
+t=0 0
+m=audio 5002 RTP/AVP 8 101
+c=IN IP4 198.51.100.10
+a=rtpmap:101 telephone-event/8000
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.10
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 0 101
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=rtpmap:101 telephone-event/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+# Learn the primary payload type while media is blocked, as in a listening room.
+rtpe_req('block media', $name, { 'from-tag' => ft(), flags => ['directional'] });
+snd($sock_a, $port_b, rtp(0, 1999, 3840, 0x5678, "\x40" x 160));
+rcv_no($sock_b);
+rtpe_req('unblock media', $name, { 'from-tag' => ft(), flags => ['directional'] });
+
+# Block the event itself so it cannot initialize the output RTP sequence.
+rtpe_req('block DTMF', $name, { 'from-tag' => ft() });
+snd($sock_a, $port_b, rtp(101 | 0x80, 2000, 4000, 0x5678, "\x0a\x07\x00\xa0"));
+# The first audio packets overlap the active event and become null discard entries.
+snd($sock_a, $port_b, rtp(0, 2001, 4000, 0x5678, "\x40" x 160));
+snd($sock_a, $port_b, rtp(0, 2002, 4160, 0x5678, "\x40" x 160));
+rcv_no($sock_b);
+rtpe_req('query', $name, { 'from-tag' => ft() });
+
+# End the event, then verify that the first real audio packet supplies the sequence
+# and subsequent packets continue normally rather than starting from zero.
+snd($sock_a, $port_b, rtp(101, 2003, 4000, 0x5678, "\x0a\x87\x01\x40"));
+snd($sock_a, $port_b, rtp(0, 2004, 4320, 0x5678, "\x40" x 160));
+snd($sock_a, $port_b, rtp(0, 2005, 4480, 0x5678, "\x40" x 160));
+# The output timestamp origin includes the suppressed interval.
+my ($ssrc) = rcv($sock_b, $port_a, rtpm(8, 2004, 4000, -1, "\x68" x 160));
+rcv($sock_b, $port_a, rtpm(8, 2005, 4160, $ssrc, "\x68" x 160));
+rtpe_req('delete', $name, { 'from-tag' => ft() });
+
+done_testing();