diff --git a/tests/content/test_prototypes.html b/tests/content/test_prototypes.html
deleted file mode 100644
index 705cff1d8dd..00000000000
--- a/tests/content/test_prototypes.html
+++ /dev/null
@@ -1,25 +0,0 @@
-<html>
-<head>
-  <meta charset="utf-8">
-  <script src="harness.js"></script>
-</head>
-<body onload="test()">
-  <foo-á>foo</foo-á>
-<script>
-function test() {
-  is_a(window.document, Node);
-  gc(); // ensure that our document rooting works; subsequent accesses should be valid.
-  is_a(window.document, Node);
-  is(window.document.nodeType, Node.DOCUMENT_NODE);
-  is_a(window.document.documentElement, Node);
-  is_a(window.document.documentElement, Element);
-  is_a(window.document.documentElement, HTMLElement);
-  is_a(window.document.documentElement, HTMLHtmlElement);
-  is_a(window.document, Document);
-  is(window.document.documentElement.tagName, "HTML");
-  is_a(window.document.getElementsByTagName('foo-á')[0], HTMLUnknownElement);
-  is(window.document.getElementsByTagName('foo-á')[0].tagName, "FOO-á");
-}
-</script>
-</body>
-</html>
diff --git a/tests/wpt/README.md b/tests/wpt/README.md
index 20cb96beda2..2d3a959f36f 100644
--- a/tests/wpt/README.md
+++ b/tests/wpt/README.md
@@ -10,13 +10,14 @@ In particular, this folder contains:
 * `include.ini`: the subset of web-platform-tests we currently run.
 * `config_css.ini`: some configuration for the CSSWG tests.
 * `include_css.ini`: the subset of the CSSWG tests we currently run.
-* `run_wpt.py` glue code to run the web-platform-tests in Servo.
-* `run_css.py` glue code to run the CSSWG tests in Servo.
-* `run.py` common code used by `run_wpt.py` and `run_css.py`.
+* `run_wpt.py`: glue code to run the web-platform-tests in Servo.
+* `run_css.py`: glue code to run the CSSWG tests in Servo.
+* `run.py`: common code used by `run_wpt.py` and `run_css.py`.
 * `web-platform-tests`: copy of the web-platform-tests.
 * `metadata`: expected failures for the web-platform-tests we run.
-* `css-tests` copy of the built CSSWG tests.
-* `metadata-css` expected failures for the CSSWG tests we run.
+* `css-tests`: copy of the built CSSWG tests.
+* `metadata-css`: expected failures for the CSSWG tests we run.
+* `mozilla`: web-platform-tests that cannot be upstreamed.
 
 Running the tests
 =================
@@ -125,3 +126,11 @@ The easiest way to update the test harness is using git:
     cd ../../..
 
 At this point you should commit the updated files in the *servo* git repository.
+
+Servo-specific tests
+====================
+
+The `mozilla` directory contains tests that cannot be upstreamed for some
+reason (e.g. because they depend on Servo-specific APIs), as well as some
+legacy tests that should be upstreamed at some point. When run they are
+mounted on the server under `/_mozilla/`.
diff --git a/tests/wpt/config.ini b/tests/wpt/config.ini
index 860912add32..3dec291038a 100644
--- a/tests/wpt/config.ini
+++ b/tests/wpt/config.ini
@@ -13,3 +13,8 @@ run-info = .
 tests = web-platform-tests
 metadata = metadata
 url-base = /
+
+[manifest:mozilla]
+tests = mozilla/tests
+metadata = mozilla/meta
+url_base = /_mozilla/
diff --git a/tests/wpt/include.ini b/tests/wpt/include.ini
index 6307f5538cf..bdbdc97fd6e 100644
--- a/tests/wpt/include.ini
+++ b/tests/wpt/include.ini
@@ -97,3 +97,5 @@ skip: true
   skip: false
 [encoding]
   skip: false
+[_mozilla]
+  skip: false
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
new file mode 100644
index 00000000000..506e7b62b7d
--- /dev/null
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -0,0 +1,23 @@
+{
+  "items": {
+    "manual": [],
+    "reftest": [],
+    "stub": [],
+    "testharness": [
+      {
+        "path": "mozilla/prototypes.html",
+        "url": "/_mozilla/mozilla/prototypes.html"
+      }
+    ],
+    "wdspec": []
+  },
+  "local_changes": {
+    "deleted": [],
+    "items": {},
+    "reftest_nodes": {}
+  },
+  "reftest_nodes": {},
+  "rev": null,
+  "url_base": "/_mozilla/",
+  "version": 2
+}
diff --git a/tests/wpt/mozilla/tests/mozilla/prototypes.html b/tests/wpt/mozilla/tests/mozilla/prototypes.html
new file mode 100644
index 00000000000..b509b46192e
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/prototypes.html
@@ -0,0 +1,26 @@
+<html>
+<head>
+  <meta charset="utf-8">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+  <foo-á>foo</foo-á>
+<script>
+test(function() {
+  assert_true(window.document instanceof Node, "Should be Node");
+  gc(); // ensure that our document rooting works; subsequent accesses should be valid.
+  assert_true(window.document instanceof Node, "Should be Node");
+  assert_equals(window.document.nodeType, Node.DOCUMENT_NODE);
+  assert_true(window.document.documentElement instanceof Node, "Should be Node");
+  assert_true(window.document.documentElement instanceof Element, "Should be Element");
+  assert_true(window.document.documentElement instanceof HTMLElement, "Should be HTMLElement");
+  assert_true(window.document.documentElement instanceof HTMLHtmlElement, "Should be HTMLHtmlElement");
+  assert_true(window.document instanceof Document, "Should be Document");
+  assert_equals(window.document.documentElement.tagName, "HTML");
+  assert_true(window.document.getElementsByTagName('foo-á')[0] instanceof HTMLUnknownElement, "Should be HTMLUnknownElement");
+  assert_equals(window.document.getElementsByTagName('foo-á')[0].tagName, "FOO-á");
+});
+</script>
+</body>
+</html>
