diff --git a/components/script/script_task.rs b/components/script/script_task.rs
index dda6faaa85b..773d43448c4 100644
--- a/components/script/script_task.rs
+++ b/components/script/script_task.rs
@@ -1671,10 +1671,32 @@ impl ScriptTask {
 
         let is_javascript = incomplete.url.scheme == "javascript";
         let parse_input = if is_javascript {
+            use url::percent_encoding::percent_decode_to;
+
+            // Turn javascript: URL into JS code to eval, according to the steps in
+            // https://html.spec.whatwg.org/multipage/#javascript-protocol
             let _ar = JSAutoRequest::new(self.get_cx());
-            let evalstr = incomplete.url.non_relative_scheme_data().unwrap();
+            let mut script_source_bytes = Vec::new();
+            // Start with the scheme data of the parsed URL (5.), while percent-decoding (8.)
+            percent_decode_to(incomplete.url.non_relative_scheme_data().unwrap().as_bytes(),
+                              &mut script_source_bytes);
+            // Append question mark and query component, if any (6.), while percent-decoding (8.)
+            if let Some(ref query) = incomplete.url.query {
+                script_source_bytes.push(b'?');
+                percent_decode_to(query.as_bytes(), &mut script_source_bytes);
+            }
+            // Append number sign and fragment component if any (7.), while percent-decoding (8.)
+            if let Some(ref fragment) = incomplete.url.fragment {
+                script_source_bytes.push(b'#');
+                percent_decode_to(fragment.as_bytes(), &mut script_source_bytes);
+            }
+
+            // UTF-8 decode (9.)
+            let script_source = String::from_utf8_lossy(&script_source_bytes);
+
+            // Script source is ready to be evaluated (11.)
             let mut jsval = RootedValue::new(self.get_cx(), UndefinedValue());
-            window.evaluate_js_on_global_with_result(evalstr, jsval.handle_mut());
+            window.evaluate_js_on_global_with_result(&script_source, jsval.handle_mut());
             let strval = DOMString::from_jsval(self.get_cx(), jsval.handle(),
                                                StringificationBehavior::Empty);
             strval.unwrap_or(DOMString::new())
diff --git a/tests/wpt/metadata/MANIFEST.json b/tests/wpt/metadata/MANIFEST.json
index f279b5f318f..22cd43f2f37 100644
--- a/tests/wpt/metadata/MANIFEST.json
+++ b/tests/wpt/metadata/MANIFEST.json
@@ -29809,7 +29809,16 @@
   },
   "local_changes": {
     "deleted": [],
-    "items": {},
+    "items": {
+      "testharness": {
+        "html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html": [
+          {
+            "path": "html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html",
+            "url": "/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html"
+          }
+        ]
+      }
+    },
     "reftest_nodes": {}
   },
   "reftest_nodes": {
diff --git a/tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html.ini b/tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html.ini
new file mode 100644
index 00000000000..f95e9c54bbe
--- /dev/null
+++ b/tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html.ini
@@ -0,0 +1,7 @@
+[javascript-url-query-fragment-components.html]
+  type: testharness
+  expected: OK
+  [iframes with javascript src]
+    expected: FAIL
+
+
diff --git a/tests/wpt/web-platform-tests/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html b/tests/wpt/web-platform-tests/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html
new file mode 100644
index 00000000000..9c18f109cd5
--- /dev/null
+++ b/tests/wpt/web-platform-tests/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-query-fragment-components.html
@@ -0,0 +1,28 @@
+<!doctype html>
+<title> javascript url with query and fragment components </title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+var a = null;
+var b = null;
+var c = null;
+</script>
+
+<iframe id="a" src='javascript:"nope" ? "yep" : "what";'></iframe>
+<iframe id="b" src='javascript:"wrong"; // # %0a "ok";'></iframe>
+<iframe id="c" src='javascript:"%252525 ? %252525 # %252525"'></iframe>
+
+<script>
+var t = async_test("iframes with javascript src", {timeout:1000});
+function check(id, expected) {
+  assert_equals(
+    document.getElementById(id).contentDocument.body.textContent,
+    expected);
+}
+onload = t.step_func(function() {
+  check("a", "yep");
+  check("b", "ok");
+  check("c", "%2525 ? %2525 # %2525");
+  t.done();
+});
+</script>