diff --git a/testing/web-platform/tests/url/resources/setters_tests.json b/testing/web-platform/tests/url/resources/setters_tests.json
index d54335f1badec..6c011e2f9acae 100644
--- a/testing/web-platform/tests/url/resources/setters_tests.json
+++ b/testing/web-platform/tests/url/resources/setters_tests.json
@@ -1848,12 +1848,30 @@
             }
         },
         {
-            "comment": "Simple percent-encoding; nuls, tabs, and newlines are removed",
+            "comment": "Simple percent-encoding; tabs and newlines are removed",
             "href": "a:/",
             "new_value": "\u0000\u0001\t\n\r\u001f !\"#$%&'()*+,-./09:;<=>?@AZ[\\]^_`az{|}~\u007f\u0080\u0081Éé",
             "expected": {
-                "href": "a:/#%01%1F%20!%22#$%&'()*+,-./09:;%3C=%3E?@AZ[\\]^_%60az{|}~%7F%C2%80%C2%81%C3%89%C3%A9",
-                "hash": "#%01%1F%20!%22#$%&'()*+,-./09:;%3C=%3E?@AZ[\\]^_%60az{|}~%7F%C2%80%C2%81%C3%89%C3%A9"
+                "href": "a:/#%00%01%1F%20!%22#$%&'()*+,-./09:;%3C=%3E?@AZ[\\]^_%60az{|}~%7F%C2%80%C2%81%C3%89%C3%A9",
+                "hash": "#%00%01%1F%20!%22#$%&'()*+,-./09:;%3C=%3E?@AZ[\\]^_%60az{|}~%7F%C2%80%C2%81%C3%89%C3%A9"
+            }
+        },
+        {
+            "comment": "Percent-encode NULLs in fragment",
+            "href": "http://example.net",
+            "new_value": "a\u0000b",
+            "expected": {
+                "href": "http://example.net/#a%00b",
+                "hash": "#a%00b"
+            }
+        },
+        {
+            "comment": "Percent-encode NULLs in fragment",
+            "href": "non-spec:/",
+            "new_value": "a\u0000b",
+            "expected": {
+                "href": "non-spec:/#a%00b",
+                "hash": "#a%00b"
             }
         },
         {
diff --git a/testing/web-platform/tests/url/resources/urltestdata.json b/testing/web-platform/tests/url/resources/urltestdata.json
index b2f8964c440da..4ffbd3cde754f 100644
--- a/testing/web-platform/tests/url/resources/urltestdata.json
+++ b/testing/web-platform/tests/url/resources/urltestdata.json
@@ -6672,7 +6672,7 @@
   {
     "input": "http://example.org/test?a#b\u0000c",
     "base": "about:blank",
-    "href": "http://example.org/test?a#bc",
+    "href": "http://example.org/test?a#b%00c",
     "protocol": "http:",
     "username": "",
     "password": "",
@@ -6681,7 +6681,35 @@
     "port": "",
     "pathname": "/test",
     "search": "?a",
-    "hash": "#bc"
+    "hash": "#b%00c"
+  },
+  {
+    "input": "non-spec://example.org/test?a#b\u0000c",
+    "base": "about:blank",
+    "href": "non-spec://example.org/test?a#b%00c",
+    "protocol": "non-spec:",
+    "username": "",
+    "password": "",
+    "host": "example.org",
+    "hostname": "example.org",
+    "port": "",
+    "pathname": "/test",
+    "search": "?a",
+    "hash": "#b%00c"
+  },
+  {
+    "input": "non-spec:/test?a#b\u0000c",
+    "base": "about:blank",
+    "href": "non-spec:/test?a#b%00c",
+    "protocol": "non-spec:",
+    "username": "",
+    "password": "",
+    "host": "",
+    "hostname": "",
+    "port": "",
+    "pathname": "/test",
+    "search": "?a",
+    "hash": "#b%00c"
   },
   "First scheme char - not allowed: https://github.com/whatwg/url/issues/464",
   {