--- a/dom/media/tests/mochitest/test_peerConnection_insertDTMF.html
+++ b/dom/media/tests/mochitest/test_peerConnection_insertDTMF.html
@@ -53,30 +53,32 @@ function insertdtmftest(pc) {
   } catch (ex) {
     threw = true;
     is(ex.code, DOMException.INVALID_STATE_ERR, "Expected InvalidStateError");
   }
   ok(threw, "Expected exception");
 }
 
 runNetworkTest(() => {
-
   test = new PeerConnectionTest();
   test.setMediaConstraints([{audio: true}], [{audio: true}]);
   test.chain.removeAfter("PC_REMOTE_WAIT_FOR_MEDIA_FLOW");
 
   // Test sender dtmf.
   test.chain.append([
     function PC_LOCAL_INSERT_DTMF(test) {
       // We want to call removeTrack
       test.pcLocal.expectNegotiationNeeded();
       return insertdtmftest(test.pcLocal._pc);
     }
   ]);
 
-  return test.run()
+  var pushPrefs = (...p) => new Promise(r => SpecialPowers.pushPrefEnv({set: p}, r));
+
+  return pushPrefs(['media.peerconnection.dtmf.enabled', true])
+    .then(() => { test.run() })
     .catch(e => ok(false, "unexpected failure: " + e));
 });
 
 </script>
 </pre>
 </body>
 </html>

--- a/dom/webidl/RTCRtpSender.webidl
+++ b/dom/webidl/RTCRtpSender.webidl
@@ -68,10 +68,11 @@ dictionary RTCRtpParameters {
 
 [Pref="media.peerconnection.enabled",
  JSImplementation="@mozilla.org/dom/rtpsender;1"]
 interface RTCRtpSender {
   readonly attribute MediaStreamTrack track;
   Promise<void> setParameters (optional RTCRtpParameters parameters);
   RTCRtpParameters getParameters();
   Promise<void> replaceTrack(MediaStreamTrack track);
+  [Pref="media.peerconnection.dtmf.enabled"]
   readonly attribute RTCDTMFSender? dtmf;
 };

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -417,16 +417,18 @@ pref("media.navigator.load_adapt.high_lo
 pref("media.navigator.load_adapt.low_load","0.40");
 pref("media.navigator.video.default_fps",30);
 pref("media.navigator.video.default_minfps",10);
 pref("media.navigator.video.use_remb", true);
 pref("media.navigator.video.use_tmmbr", false);
 pref("media.navigator.audio.use_fec", true);
 pref("media.navigator.video.red_ulpfec_enabled", false);
 
+pref("media.peerconnection.dtmf.enabled", false);
+
 pref("media.webrtc.debug.trace_mask", 0);
 pref("media.webrtc.debug.multi_log", false);
 pref("media.webrtc.debug.aec_log_dir", "");
 pref("media.webrtc.debug.log_file", "");
 pref("media.webrtc.debug.aec_dump_max_size", 4194304); // 4MB
 
 #ifdef MOZ_WIDGET_GONK
 pref("media.navigator.video.default_width", 320);