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diff --git a/dom/html/test/dialog/test_bug1648877_dialog_fullscreen_denied.html b/dom/html/test/dialog/test_bug1648877_dialog_fullscreen_denied.html
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index 0000000000..906c7dd53e
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+++ b/dom/html/test/dialog/test_bug1648877_dialog_fullscreen_denied.html
@@ -0,0 +1,52 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1648877
+-->
+<head>
+  <title>Test for Bug 1648877</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+  <a target="_blank"
+     href="https://bugzilla.mozilla.org/show_bug.cgi?id=1648877">Requesting
+  fullscreen a dialog element should be denied</a>
+<p id="display"></p>
+<dialog>
+</dialog>
+<div style="width: 30px; height:30px" </div>
+    
+<pre id="test">
+<script type="application/javascript">
+SimpleTest.waitForExplicitFinish();
+
+function runTest() {
+  document.addEventListener("fullscreenchange", () => {
+    ok(false, "Should never receive " +
+      "a fullscreenchange event in the main window.");
+  });
+
+  document.addEventListener('fullscreenerror', (event) => {
+    ok(!document.fullscreenElement,
+       "Should not grant request if the element is dialog");
+    SimpleTest.finish();
+  });
+
+  const div = document.querySelector("div");
+
+  div.addEventListener("click", function() {
+    const dialog = document.querySelector("dialog");
+    dialog.requestFullscreen();
+  });
+
+  synthesizeMouseAtCenter(div, {});
+}
+
+SimpleTest.waitForFocus(runTest);
+
+</script>
+</pre>
+</body>
+</html>