--- a/dom/media/test/test_texttrackcue.html
+++ b/dom/media/test/test_texttrackcue.html
@@ -238,17 +238,17 @@ SpecialPowers.pushPrefEnv({"set": [["med
 
       video.addEventListener("timeupdate", function() {
         var activeCues = trackElement.track.activeCues,
             found = false,
             playbackTime = video.currentTime;
 
         for (var i = 0; i < cueInfo.length; i++) {
           var cue = cueInfo[i];
-          if (playbackTime >= cue.startTime && playbackTime <= cue.endTime) {
+          if (playbackTime >= cue.startTime && playbackTime < cue.endTime) {
             is(activeCues.length, cue.ids.length, "There should be " + cue.ids.length + " currently active cue(s).");
             for (var j = 0; j < cue.ids.length; j++) {
               isnot(activeCues.getCueById(cue.ids[j]), undefined, "The cue with ID " + cue.ids[j] + " should be active.");
             }
             break;
           }
         }
       });