diff --git a/components/script/dom/urlsearchparams.rs b/components/script/dom/urlsearchparams.rs
index d3c7ae93b63..5be91c9304c 100644
--- a/components/script/dom/urlsearchparams.rs
+++ b/components/script/dom/urlsearchparams.rs
@@ -54,9 +54,17 @@ impl URLSearchParams {
         match init {
             Some(USVStringOrURLSearchParams::USVString(init)) => {
                 // Step 2.
-                *query.list.borrow_mut() = form_urlencoded::parse(init.0.as_bytes())
-                    .into_owned()
-                    .collect();
+                let init_bytes = match init.0.chars().next() {
+                    Some(first_char) if first_char == '?' => {
+                        let (_, other_bytes) = init.0.as_bytes().split_at(1);
+
+                        other_bytes
+                    },
+                    _ => init.0.as_bytes(),
+                };
+
+                *query.list.borrow_mut() =
+                    form_urlencoded::parse(init_bytes).into_owned().collect();
             },
             Some(USVStringOrURLSearchParams::URLSearchParams(init)) => {
                 // Step 3.
diff --git a/tests/wpt/metadata/MANIFEST.json b/tests/wpt/metadata/MANIFEST.json
index 1e9d2483f38..49b4d8c67cd 100644
--- a/tests/wpt/metadata/MANIFEST.json
+++ b/tests/wpt/metadata/MANIFEST.json
@@ -674610,7 +674610,7 @@
    "testharness"
   ],
   "url/urlsearchparams-constructor.any.js": [
-   "6fff03f00fdddd915f91bbec7973ebc1326b3b5a",
+   "398021dde2f35f427399c639871bfbb8106a3279",
    "testharness"
   ],
   "url/urlsearchparams-delete.any.js": [
diff --git a/tests/wpt/web-platform-tests/url/urlsearchparams-constructor.any.js b/tests/wpt/web-platform-tests/url/urlsearchparams-constructor.any.js
index 6fff03f00fd..398021dde2f 100644
--- a/tests/wpt/web-platform-tests/url/urlsearchparams-constructor.any.js
+++ b/tests/wpt/web-platform-tests/url/urlsearchparams-constructor.any.js
@@ -14,6 +14,11 @@ test(function() {
     assert_equals(params.toString(), "")
 }, "URLSearchParams constructor, no arguments")
 
+test(function () {
+    var params = new URLSearchParams("?a=b")
+    assert_equals(params.toString(), "a=b")
+}, 'URLSearchParams constructor, remove leading "?"')
+
 test(() => {
     var params = new URLSearchParams(DOMException);
     assert_equals(params.toString(), "INDEX_SIZE_ERR=1&DOMSTRING_SIZE_ERR=2&HIERARCHY_REQUEST_ERR=3&WRONG_DOCUMENT_ERR=4&INVALID_CHARACTER_ERR=5&NO_DATA_ALLOWED_ERR=6&NO_MODIFICATION_ALLOWED_ERR=7&NOT_FOUND_ERR=8&NOT_SUPPORTED_ERR=9&INUSE_ATTRIBUTE_ERR=10&INVALID_STATE_ERR=11&SYNTAX_ERR=12&INVALID_MODIFICATION_ERR=13&NAMESPACE_ERR=14&INVALID_ACCESS_ERR=15&VALIDATION_ERR=16&TYPE_MISMATCH_ERR=17&SECURITY_ERR=18&NETWORK_ERR=19&ABORT_ERR=20&URL_MISMATCH_ERR=21&QUOTA_EXCEEDED_ERR=22&TIMEOUT_ERR=23&INVALID_NODE_TYPE_ERR=24&DATA_CLONE_ERR=25")