diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index a29a6bb5c5a..f556de3c784 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -13515,6 +13515,12 @@
      {}
     ]
    ],
+   "mozilla/partial_shadow_dom.html": [
+    [
+     "mozilla/partial_shadow_dom.html",
+     {}
+    ]
+   ],
    "mozilla/postmessage_closed.html": [
     [
      "mozilla/postmessage_closed.html",
@@ -20430,6 +20436,10 @@
    "5aff666995fe6cd1d4e84e63a9f6019d04387f8e",
    "testharness"
   ],
+  "mozilla/partial_shadow_dom.html": [
+   "d97f1422d20161e989f200d44be6e379f79410bd",
+   "testharness"
+  ],
   "mozilla/poster.png": [
    "33834c3ef095fa9c0080017e1b65b2eb8413eac4",
    "support"
diff --git a/tests/wpt/mozilla/meta/mozilla/partial_shadow_dom.html.ini b/tests/wpt/mozilla/meta/mozilla/partial_shadow_dom.html.ini
new file mode 100644
index 00000000000..6b14e5081c1
--- /dev/null
+++ b/tests/wpt/mozilla/meta/mozilla/partial_shadow_dom.html.ini
@@ -0,0 +1,2 @@
+[partial_shadow_dom.html]
+  prefs: [dom.shadowdom.enabled:true]
diff --git a/tests/wpt/mozilla/tests/mozilla/partial_shadow_dom.html b/tests/wpt/mozilla/tests/mozilla/partial_shadow_dom.html
new file mode 100644
index 00000000000..d97f1422d20
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/partial_shadow_dom.html
@@ -0,0 +1,38 @@
+<!doctype html>
+<head>
+  <meta charset="utf-8">
+  <title></title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+  <h1 class="header">Not in the shadows</h1>
+  <div id="host">
+  </div>
+  <script>
+    test(function() {
+      // Attach shadow.
+      var host = document.getElementById('host');
+      var shadowRoot = host.attachShadow();
+      assert_not_equals(shadowRoot, null);
+      assert_equals(shadowRoot.host, host);
+      assert_equals(shadowRoot.mode, 'closed');
+
+      assert_equals(document.body.getElementsByTagName('h1').length, 1);
+      assert_equals(document.body.getElementsByClassName('header').length, 1);
+      assert_equals(document.querySelectorAll('h1').length, 1);
+      assert_equals(document.body.childNodes.length, 6);
+
+      // Append child to shadow tree and check that its content is encapsulated.
+      var shadowChild = document.createElement('h1');
+      shadowChild.classList.add('header');
+      shadowChild.textContent = 'In the shadows';
+      shadowRoot.appendChild(shadowChild);
+      assert_equals(document.body.getElementsByTagName('h1').length, 1);
+      assert_equals(document.body.getElementsByClassName('header').length, 1);
+      assert_equals(document.querySelectorAll('h1').length, 1);
+      assert_equals(document.body.childNodes.length, 6);
+      assert_equals(shadowRoot.querySelectorAll('h1').length, 1);
+    });
+  </script>
+</body>
