--- a/dom/media/tests/mochitest/test_getUserMedia_loadedmetadata.html
+++ b/dom/media/tests/mochitest/test_getUserMedia_loadedmetadata.html
@@ -13,16 +13,17 @@
   /**
    * Tests that assigning a stream to a media element results in the
    * "loadedmetadata" event without having to play() the media element.
    *
    * Also makes sure that the video size has been set on "loadedmetadata".
    */
   runTest(function () {
     var v = document.createElement("video");
+    document.body.appendChild(v);
     v.preload = "metadata";
 
     var constraints = {video: true, audio: true};
     return getUserMedia(constraints).then(stream => new Promise(resolve => {
       v.srcObject = stream;
       v.onloadedmetadata = resolve;
     })).then(() => {
       isnot(v.videoWidth, 0, "videoWidth shall be set on 'loadedmetadata'");