--- a/dom/media/tests/mochitest/head.js
+++ b/dom/media/tests/mochitest/head.js
@@ -843,17 +843,20 @@ VideoStreamHelper.prototype = {
     return addFinallyToPromise(timeout(
       Promise.all([
         this._helper.waitForPixelColor(canvas, this._helper.green, 128,
                                        canvas.id + " should become green"),
         this._helper.waitForPixelColor(canvas, this._helper.red, 128,
                                        canvas.id + " should become red")
       ]),
       timeout_value,
-      "Timed out waiting for frames")).finally(() => clearInterval(intervalId));
+      "Timed out waiting for frames")).finally(() => {
+        ok(false, "Waiting for red and green timed out");
+        clearInterval(intervalId);
+        });
   },
 
   verifyNoFrames: function(canvas) {
     return this.waitForFrames(canvas).then(
       () => ok(false, "Color should not change"),
       () => ok(true, "Color should not change")
     );
   }