diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 084394e7ef9..48b748bd81c 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -7094,6 +7094,12 @@
             "url": "/_mozilla/mozilla/load_event.html"
           }
         ],
+        "mozilla/localeCompare.html": [
+          {
+            "path": "mozilla/localeCompare.html",
+            "url": "/_mozilla/mozilla/localeCompare.html"
+          }
+        ],
         "mozilla/mime_sniffing_font_context.html": [
           {
             "path": "mozilla/mime_sniffing_font_context.html",
diff --git a/tests/wpt/mozilla/tests/mozilla/localeCompare.html b/tests/wpt/mozilla/tests/mozilla/localeCompare.html
new file mode 100644
index 00000000000..c6042d8739e
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/localeCompare.html
@@ -0,0 +1,10 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>localeCompare should return the same as other browsers, even though it's implementation-dependent</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(function() {
+  assert_equals("ab".localeCompare("aZ"), -1);
+})
+</script>
