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diff --git a/testing/web-platform/tests/html/semantics/interactive-elements/the-dialog-element/top-layer-nesting.html b/testing/web-platform/tests/html/semantics/interactive-elements/the-dialog-element/top-layer-nesting.html
new file mode 100644
index 0000000000..9e0616e952
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+++ b/testing/web-platform/tests/html/semantics/interactive-elements/the-dialog-element/top-layer-nesting.html
@@ -0,0 +1,66 @@
+<!DOCTYPE html>
+<html>
+<head>
+<link rel="match" href="top-layer-nesting-ref.html">
+<link rel="help" href="https://fullscreen.spec.whatwg.org/#new-stacking-layer">
+<style>
+dialog {
+    height: 150px;
+    width: 150px;
+    outline: none;
+}
+
+::backdrop {
+    display: none;
+}
+
+#bottomDialog {
+    background-color: yellow;
+    top: 100px;
+    z-index: 1000;
+}
+
+#middleDialog {
+    background-color: blue;
+    top: 150px;
+    left: 50px;
+    z-index: -500;
+}
+
+#topDialog {
+    background-color: green;
+    top: 200px;
+    left: 100px;
+    z-index: -1000;
+}
+
+.red {
+    background-color: red;
+    top: 250px;
+    left: 0px;
+}
+</style>
+</head>
+<body>
+This tests that top layer elements are stacked correctly even if nested in the DOM tree.
+The test passes if you see no red rectangles and see 3 rectangles stacked in the following order (from bottom to top): yellow, blue, green.
+
+<dialog id="topDialog">
+    <dialog id="middleDialog">
+        <dialog id="bottomDialog">
+            <dialog id="hiddenDialog" class="red">
+                <dialog id="hiddenDialogChild" class="red"></dialog>
+            </dialog>
+        </dialog>
+    </dialog>
+</dialog>
+<script>
+document.getElementById('hiddenDialogChild').showModal();
+document.getElementById('hiddenDialog').showModal();
+document.getElementById('bottomDialog').showModal();
+document.getElementById('middleDialog').showModal();
+document.getElementById('topDialog').showModal();
+document.getElementById('hiddenDialog').close();
+</script>
+</body>
+</html>