diff --git a/lib/ex_webrtc/rtp_sender.ex b/lib/ex_webrtc/rtp_sender.ex
index f61063e4..6acd3ace 100644
--- a/lib/ex_webrtc/rtp_sender.ex
+++ b/lib/ex_webrtc/rtp_sender.ex
@@ -134,12 +134,6 @@ defmodule ExWebRTC.RTPSender do
   @doc false
   @spec send_packet(sender(), ExRTP.Packet.t(), boolean()) :: {binary(), sender()}
   def send_packet(sender, packet, rtx?) do
-    %Extmap{} = mid_extmap = Map.fetch!(sender.rtp_hdr_exts, @mid_uri)
-
-    mid_ext =
-      %ExRTP.Packet.Extension.SourceDescription{text: sender.mid}
-      |> ExRTP.Packet.Extension.SourceDescription.to_raw(mid_extmap.id)
-
     {pt, ssrc} =
       if rtx? do
         {sender.rtx_pt, sender.rtx_ssrc}
@@ -147,10 +141,25 @@ defmodule ExWebRTC.RTPSender do
         {sender.pt, sender.ssrc}
       end
 
+    packet = %{packet | payload_type: pt, ssrc: ssrc}
+
+    # Add mid header extension only if it was negotiated.
+    # The receiver can still demux packets based
+    # on ssrc (if it was included in sdp) or payload type
     packet =
-      %{packet | payload_type: pt, ssrc: ssrc}
-      |> ExRTP.Packet.remove_extension(mid_extmap.id)
-      |> ExRTP.Packet.add_extension(mid_ext)
+      case Map.get(sender.rtp_hdr_exts, @mid_uri) do
+        %Extmap{} = mid_extmap ->
+          mid_ext =
+            %ExRTP.Packet.Extension.SourceDescription{text: sender.mid}
+            |> ExRTP.Packet.Extension.SourceDescription.to_raw(mid_extmap.id)
+
+          packet
+          |> ExRTP.Packet.remove_extension(mid_extmap.id)
+          |> ExRTP.Packet.add_extension(mid_ext)
+
+        nil ->
+          packet
+      end
 
     report_recorder =
       if sender.reports? do
diff --git a/test/ex_webrtc/dtls_transport_test.exs b/test/ex_webrtc/dtls_transport_test.exs
index 5d473f2d..69d90732 100644
--- a/test/ex_webrtc/dtls_transport_test.exs
+++ b/test/ex_webrtc/dtls_transport_test.exs
@@ -9,6 +9,10 @@ defmodule ExWebRTC.DTLSTransportTest do
                |> ExDTLS.get_cert_fingerprint()
                |> Utils.hex_dump()
 
+  @rtp_header <<1::1, 0::1, 0::1, 0::1, 0::4, 0::1, 96::7, 1::16, 1::32, 1::32>>
+  @rtp_payload <<0>>
+  @rtp_packet <<@rtp_header::binary, @rtp_payload::binary>>
+
   defmodule MockICETransport do
     @behaviour ExWebRTC.ICETransport
 
@@ -175,6 +179,10 @@ defmodule ExWebRTC.DTLSTransportTest do
     assert :ok = check_handshake(dtls, ice_transport, ice_pid, remote_dtls)
     assert_receive {:dtls_transport, ^dtls, {:state_change, :connecting}}
     assert_receive {:dtls_transport, ^dtls, {:state_change, :connected}}
+
+    # assert we can send rtp packets
+    assert :ok = DTLSTransport.send_rtp(dtls, @rtp_packet)
+    assert_receive {:mock_ice, <<@rtp_header::binary, _payload::binary>>}
   end
 
   test "finishes handshake in passive mode", %{
@@ -200,6 +208,39 @@ defmodule ExWebRTC.DTLSTransportTest do
     assert :ok == check_handshake(dtls, ice_transport, ice_pid, remote_dtls)
     assert_receive {:dtls_transport, ^dtls, {:state_change, :connecting}}
     assert_receive {:dtls_transport, ^dtls, {:state_change, :connected}}
+
+    # assert we can send rtp packets
+    assert :ok = DTLSTransport.send_rtp(dtls, @rtp_packet)
+    assert_receive {:mock_ice, <<@rtp_header::binary, _payload::binary>>}
+  end
+
+  test "drops packets when packet loss is set", %{
+    dtls: dtls,
+    ice_transport: ice_transport,
+    ice_pid: ice_pid
+  } do
+    :ok = DTLSTransport.start_dtls(dtls, :active, @fingerprint)
+    remote_dtls = ExDTLS.init(mode: :server, dtls_srtp: true)
+
+    :ok = DTLSTransport.set_ice_connected(dtls)
+
+    assert :ok = check_handshake(dtls, ice_transport, ice_pid, remote_dtls)
+    assert_receive {:dtls_transport, ^dtls, {:state_change, :connecting}}
+    assert_receive {:dtls_transport, ^dtls, {:state_change, :connected}}
+
+    # assert we can send data
+    DTLSTransport.send_rtp(dtls, @rtp_packet)
+    assert_receive {:mock_ice, <<@rtp_header::binary, _payload::binary>>}
+
+    # now set packet-loss
+    DTLSTransport.set_packet_loss(dtls, 100)
+    DTLSTransport.send_rtp(dtls, @rtp_packet)
+    refute_receive {:mock_ice, _rtp_packet}
+  end
+
+  test "stop/1", %{dtls: dtls} do
+    assert :ok == DTLSTransport.stop(dtls)
+    assert false == Process.alive?(dtls)
   end
 
   defp check_handshake(dtls, ice_transport, ice_pid, remote_dtls) do
@@ -218,9 +259,4 @@ defmodule ExWebRTC.DTLSTransportTest do
         :ok
     end
   end
-
-  test "stop/1", %{dtls: dtls} do
-    assert :ok == DTLSTransport.stop(dtls)
-    assert false == Process.alive?(dtls)
-  end
 end