--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -639275,17 +639275,17 @@
    "abcb2970b63f48f2e817d2b5ff8f085e02df7588",
    "support"
   ],
   "tools/serve/serve.py": [
    "30791eb967b36ac9a3c85070b232b4459723ef2d",
    "support"
   ],
   "tools/serve/test_serve.py": [
-   "e939c3a0ccee4ac4f5babbcab3b9d30dbfa80be8",
+   "1c089b506738ee73e2f1e29cf1729a1abc1e0c0b",
    "support"
   ],
   "tools/third_party/atomicwrites/.gitignore": [
    "2b2d3128753e9f6f34895e7183595829d1063a5a",
    "support"
   ],
   "tools/third_party/atomicwrites/.travis.yml": [
    "e9779018ad31e6210a8d91ebe18c9cab0ec03fdd",

--- a/testing/web-platform/tests/tools/serve/test_serve.py
+++ b/testing/web-platform/tests/tools/serve/test_serve.py
@@ -30,17 +30,17 @@ def test_make_hosts_file_nix():
 
 @pytest.mark.skipif(platform.uname()[0] != "Windows",
                     reason="Expected contents are platform-dependent")
 def test_make_hosts_file_windows():
     with ConfigBuilder(ports={"http": [8000]},
                        browser_host="foo.bar",
                        alternate_hosts={"alt": "foo2.bar"},
                        subdomains={"a", "b"},
-                       not_subdomains={"x, y"}) as c:
+                       not_subdomains={"x", "y"}) as c:
         hosts = serve.make_hosts_file(c, "192.168.42.42")
         lines = hosts.split("\n")
         assert set(lines) == {"",
                               "0.0.0.0\tx.foo.bar",
                               "0.0.0.0\tx.foo2.bar",
                               "0.0.0.0\ty.foo.bar",
                               "0.0.0.0\ty.foo2.bar",
                               "192.168.42.42\tfoo.bar",