--- a/testing/web-platform/tests/webrtc/RTCDTMFSender-helper.js
+++ b/testing/web-platform/tests/webrtc/RTCDTMFSender-helper.js
@@ -71,17 +71,17 @@ function test_tone_change_events(testFun
           `Expect current event.tone to be ${expectedTone}`);
 
         assert_equals(dtmfSender.toneBuffer, expectedToneBuffer,
           `Expect dtmfSender.toneBuffer to be updated to ${expectedToneBuffer}`);
 
         const now = Date.now();
         const duration = now - lastEventTime;
 
-        assert_approx_equals(duration, expectedDuration, 50,
+        assert_approx_equals(duration, expectedDuration, 150,
           `Expect tonechange event for "${tone}" to be fired approximately after ${expectedDuration} seconds`);
 
         lastEventTime = now;
 
         if(toneChanges.length === 0) {
           // Wait for same duration as last expected duration + 100ms
           // before passing test in case there are new tone events fired,
           // in which case the test should fail.