diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index d94defbd2d7..3297053b159 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -4636,6 +4636,18 @@
             "url": "/_mozilla/css/removeproperty.html"
           }
         ],
+        "css/restyle-nth-child.html": [
+          {
+            "path": "css/restyle-nth-child.html",
+            "references": [
+              [
+                "/_mozilla/css/restyle-nth-child-ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/restyle-nth-child.html"
+          }
+        ],
         "css/restyle_hints_attr.html": [
           {
             "path": "css/restyle_hints_attr.html",
@@ -14006,6 +14018,18 @@
           "url": "/_mozilla/css/removeproperty.html"
         }
       ],
+      "css/restyle-nth-child.html": [
+        {
+          "path": "css/restyle-nth-child.html",
+          "references": [
+            [
+              "/_mozilla/css/restyle-nth-child-ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/restyle-nth-child.html"
+        }
+      ],
       "css/restyle_hints_attr.html": [
         {
           "path": "css/restyle_hints_attr.html",
diff --git a/tests/wpt/mozilla/tests/css/restyle-nth-child-ref.html b/tests/wpt/mozilla/tests/css/restyle-nth-child-ref.html
new file mode 100644
index 00000000000..c59c9fde35c
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/restyle-nth-child-ref.html
@@ -0,0 +1,17 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>CSS test reference.</title>
+<style>
+  .container div {
+    width: 50px;
+    height: 50px;
+    background: blue;
+  }
+  .container div:nth-child(2) {
+    background: green;
+  }
+</style>
+<div class="container">
+  <div></div>
+  <div></div>
+</div>
diff --git a/tests/wpt/mozilla/tests/css/restyle-nth-child.html b/tests/wpt/mozilla/tests/css/restyle-nth-child.html
new file mode 100644
index 00000000000..b7e1fb4b461
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/restyle-nth-child.html
@@ -0,0 +1,24 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Restyling of a child of a parent that didn't match nth-child but now
+  does should be correct.</title>
+<link rel="match" href="restyle-nth-child-ref.html">
+<style>
+  .container div {
+    width: 50px;
+    height: 50px;
+    background: blue;
+  }
+  .container div:nth-child(2) {
+    background: green;
+  }
+</style>
+<div class="container">
+  <div></div>
+</div>
+<script>
+  let container = document.querySelector('.container');
+  window.onload = function() {
+    container.insertBefore(document.createElement('div'), container.firstChild);
+  }
+</script>
