diff --git a/t/Makefile b/t/Makefile
index 8dca8baaf..801766189 100644
--- a/t/Makefile
+++ b/t/Makefile
@@ -223,6 +223,9 @@ daemon-tests-audio-player-play-media:	daemon-test-deps
 daemon-tests-rtpp-flags:	daemon-test-deps
 	./auto-test-helper "$@" perl -I../perl auto-daemon-tests-rtpp-flags.pl
 
+daemon-tests-unknown-fmtp:	daemon-test-deps
+	./auto-test-helper "$@" perl -I../perl auto-daemon-tests-unknown-fmtp.pl
+
 daemon-tests-sdp-manipulations:	daemon-test-deps
 	./auto-test-helper "$@" perl -I../perl auto-daemon-tests-sdp-manipulations.pl
 
diff --git a/t/auto-daemon-tests-unknown-fmtp.pl b/t/auto-daemon-tests-unknown-fmtp.pl
new file mode 100644
index 000000000..272dd99df
--- /dev/null
+++ b/t/auto-daemon-tests-unknown-fmtp.pl
@@ -0,0 +1,210 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use NGCP::Rtpengine::Test;
+use NGCP::Rtpclient::SRTP;
+use NGCP::Rtpengine::AutoTest;
+use Test::More;
+use NGCP::Rtpclient::ICE;
+use POSIX;
+
+autotest_start(qw(--config-file=none -t -1 -i 203.0.113.1 -i 2001:db8:4321::1
+			-i foo/203.0.113.7 -i bar/203.0.113.8
+			-n 2223 -c 12345 -f -L 7 -E -u 2222 --silence-detect=1 --log-level-internals=7))
+		or die;
+
+new_call;
+
+offer('rtpp-flags: basic A to B call', { 
+    'rtpp-flags' => 'replace-origin address-family=IP4 transport-protocol=RTP/AVP',
+    'from-tag' => ft(),
+    }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 2000 RTP/AVP 0 8 101
+a=rtpmap:0 PCMU/8000
+a=fmtp:0 this-is-unknown=no
+a=rtpmap:8 PCMA/8000
+a=fmtp:8 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 203.0.113.1
+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=fmtp:0 this-is-unknown=no
+a=rtpmap:8 PCMA/8000
+a=fmtp:8 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+#  g711 SDP answer fmtp will ingore
+
+answer('rtpp-flags: basic A to B call', { 
+    'rtpp-flags' => 'replace-origin address-family=IP4 transport-protocol=RTP/AVP',
+     'from-tag' => ft(),
+     'to-tag' => tt(),
+    }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/AVP 0 101
+a=rtpmap:0 PCMU/8000
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 203.0.113.1
+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=fmtp:101 0-15
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('rtpp-flags: basic A to B call', { 
+    'rtpp-flags' => 'replace-origin address-family=IP4 transport-protocol=RTP/AVP',
+    'from-tag' => ft(),
+    }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 2000 RTP/AVP 3 101
+a=rtpmap:3 GSM/8000
+a=fmtp:3 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 203.0.113.1
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 3 101
+c=IN IP4 203.0.113.1
+a=rtpmap:3 GSM/8000
+a=fmtp:3 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+# answer without a=fmtp:3 this-is-unknown=no, GSM will be removed, no audio codec now
+answer('rtpp-flags: basic A to B call', { 
+    'rtpp-flags' => 'replace-origin address-family=IP4 transport-protocol=RTP/AVP',
+     'from-tag' => ft(),
+     'to-tag' => tt(),
+    }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/AVP 3 101
+a=rtpmap:3 GSM/8000
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 203.0.113.1
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 101
+c=IN IP4 203.0.113.1
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('rtpp-flags: basic A to B call', { 
+    'rtpp-flags' => 'replace-origin address-family=IP4 transport-protocol=RTP/AVP',
+    'from-tag' => ft(),
+    }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.1
+s=tester
+t=0 0
+m=audio 2000 RTP/AVP 3 101
+a=rtpmap:3 GSM/8000
+a=fmtp:3 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+c=IN IP4 198.51.100.1
+a=sendrecv
+----------------------------------
+v=0
+o=- 1545997027 1 IN IP4 203.0.113.1
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 3 101
+c=IN IP4 203.0.113.1
+a=rtpmap:3 GSM/8000
+a=fmtp:3 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+# answer with a=fmtp:3 this-is-unknown=no, GSM will be keeped
+answer('rtpp-flags: basic A to B call', { 
+    'rtpp-flags' => 'replace-origin address-family=IP4 transport-protocol=RTP/AVP',
+     'from-tag' => ft(),
+     'to-tag' => tt(),
+    }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.3
+s=tester
+t=0 0
+m=audio 2002 RTP/AVP 3 101
+a=rtpmap:3 GSM/8000
+a=fmtp:3 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+c=IN IP4 198.51.100.3
+a=sendrecv
+--------------------------------------
+v=0
+o=- 1545997027 1 IN IP4 203.0.113.1
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 3 101
+c=IN IP4 203.0.113.1
+a=rtpmap:3 GSM/8000
+a=fmtp:3 this-is-unknown=no
+a=rtpmap:101 telephone-event/8000
+a=fmtp:101 0-15
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+#done_testing;NGCP::Rtpengine::AutoTest::terminate('f00');exit;
+done_testing();