--- a/testing/web-platform/tests/tools/manifest/manifest.py
+++ b/testing/web-platform/tests/tools/manifest/manifest.py
@@ -46,16 +46,25 @@ class Manifest(object):
             for path, tests in sorted(iteritems(self._data[item_type])):
                 yield item_type, path, tests
 
     def iterpath(self, path):
         for type_tests in self._data.values():
             for test in type_tests.get(path, set()):
                 yield test
 
+    def iterdir(self, dir_name):
+        if not dir_name.endswith(os.path.sep):
+            dir_name = dir_name + os.path.sep
+        for type_tests in self._data.values():
+            for path, tests in type_tests.iteritems():
+                if path.startswith(dir_name):
+                    for test in tests:
+                        yield test
+
     @property
     def reftest_nodes_by_url(self):
         if self._reftest_nodes_by_url is None:
             by_url = {}
             for path, nodes in iteritems(self._data.get("reftests", {})):
                 for node in nodes:
                     by_url[node.url] = node
             self._reftest_nodes_by_url = by_url

--- a/testing/web-platform/tests/tools/wptrunner/wptrunner/manifestinclude.py
+++ b/testing/web-platform/tests/tools/wptrunner/wptrunner/manifestinclude.py
@@ -88,17 +88,18 @@ class IncludeManifest(ManifestItem):
         paths = glob.glob(maybe_path)
 
         if paths:
             urls = []
             for path in paths:
                 for manifest, data in test_manifests.iteritems():
                     found = False
                     rel_path = os.path.relpath(path, data["tests_path"])
-                    for test in manifest.iterpath(rel_path):
+                    iterator = manifest.iterpath if os.path.isfile(path) else manifest.iterdir
+                    for test in iterator(rel_path):
                         if not hasattr(test, "url"):
                             continue
                         url = test.url
                         if query or fragment:
                             parsed = urlparse.urlparse(url)
                             if ((query and query != parsed.query) or
                                 (fragment and fragment != parsed.fragment)):
                                 continue