diff --git a/components/script/dom/urlsearchparams.rs b/components/script/dom/urlsearchparams.rs
index 0c234cb2664..1e418c4b6f8 100644
--- a/components/script/dom/urlsearchparams.rs
+++ b/components/script/dom/urlsearchparams.rs
@@ -140,7 +140,7 @@ impl URLSearchParamsHelpers for URLSearchParams {
 
                     // Encode everything else using 'percented-encoded bytes'
                     // https://url.spec.whatwg.org/#percent-encode
-                    a => format!("%{:X}", a).into_bytes(),
+                    a => format!("%{:02X}", a).into_bytes(),
                 };
                 buf.push_all(&append);
             }
diff --git a/tests/wpt/metadata/XMLHttpRequest/send-usp.html.ini b/tests/wpt/metadata/XMLHttpRequest/send-usp.html.ini
deleted file mode 100644
index 4167953af31..00000000000
--- a/tests/wpt/metadata/XMLHttpRequest/send-usp.html.ini
+++ /dev/null
@@ -1,50 +0,0 @@
-[send-usp.html]
-  type: testharness
-  [XMLHttpRequest.send(URLSearchParams) (0)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (1)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (2)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (3)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (4)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (5)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (6)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (7)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (8)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (9)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (10)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (11)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (12)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (13)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (14)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (15)]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/XMLHttpRequest/send-usp.worker.js.ini b/tests/wpt/metadata/XMLHttpRequest/send-usp.worker.js.ini
deleted file mode 100644
index 420778a82e9..00000000000
--- a/tests/wpt/metadata/XMLHttpRequest/send-usp.worker.js.ini
+++ /dev/null
@@ -1,50 +0,0 @@
-[send-usp.worker]
-  type: testharness
-  [XMLHttpRequest.send(URLSearchParams) (0)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (1)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (2)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (3)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (4)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (5)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (6)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (7)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (8)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (9)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (10)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (11)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (12)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (13)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (14)]
-    expected: FAIL
-
-  [XMLHttpRequest.send(URLSearchParams) (15)]
-    expected: FAIL
-