diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 0820a51a18b..18329c0c5f3 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -75,6 +75,18 @@
             "url": "/_mozilla/css/class-namespaces.html"
           }
         ],
+        "css/setpropertypriority.html": [
+          {
+            "path": "css/setpropertypriority.html",
+            "references": [
+              [
+                "/_mozilla/css/setpropertypriority_ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/setpropertypriority.html"
+          }
+        ],
         "mozilla/canvas/drawimage_html_image_1.html": [
           {
             "path": "mozilla/canvas/drawimage_html_image_1.html",
@@ -800,6 +812,18 @@
           "url": "/_mozilla/css/class-namespaces.html"
         }
       ],
+      "css/setpropertypriority.html": [
+        {
+          "path": "css/setpropertypriority.html",
+          "references": [
+            [
+              "/_mozilla/css/setpropertypriority_ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/setpropertypriority.html"
+        }
+      ],
       "mozilla/canvas/drawimage_html_image_1.html": [
         {
           "path": "mozilla/canvas/drawimage_html_image_1.html",
diff --git a/tests/wpt/mozilla/tests/css/setpropertypriority.html b/tests/wpt/mozilla/tests/css/setpropertypriority.html
new file mode 100644
index 00000000000..5cbceacef35
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/setpropertypriority.html
@@ -0,0 +1,9 @@
+<link rel=match href=setpropertypriority_ref.html>
+<body>
+<p id="hello" style="color: green">This text should be green.</p>
+<style>
+  #hello { color: red !important }
+</style>
+<script>
+  document.getElementById("hello").style.setPropertyPriority("color", "important");
+</script>
diff --git a/tests/wpt/mozilla/tests/css/setpropertypriority_ref.html b/tests/wpt/mozilla/tests/css/setpropertypriority_ref.html
new file mode 100644
index 00000000000..97cd81b31bf
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/setpropertypriority_ref.html
@@ -0,0 +1 @@
+<p style="color: green">This text should be green.
