diff --git a/core/lib/Drupal/Core/Url.php b/core/lib/Drupal/Core/Url.php
index 7add013..5d9b3da 100644
--- a/core/lib/Drupal/Core/Url.php
+++ b/core/lib/Drupal/Core/Url.php
@@ -298,7 +298,7 @@ public static function fromUri($uri, $options = []) {
     if ($uri_parts === FALSE) {
       throw new \InvalidArgumentException(SafeMarkup::format('The URI "@uri" is malformed.', ['@uri' => $uri]));
     }
-    // Support for protocol-relative URLs.
+    // Support for scheme-relative URLs.
     if (empty($uri_parts['scheme']) &&  strpos($uri, '//') === 0) {
       $uri_parts['scheme'] = 'relative';
     }
diff --git a/core/modules/menu_ui/src/Tests/MenuTest.php b/core/modules/menu_ui/src/Tests/MenuTest.php
index e826a05..b99d66a 100644
--- a/core/modules/menu_ui/src/Tests/MenuTest.php
+++ b/core/modules/menu_ui/src/Tests/MenuTest.php
@@ -588,10 +588,10 @@ public function testMenuSchemeRelative() {
 
     // Make a path with query and fragment on.
     $path = '//drupal.org';
-    $item = $this->addMenuLink(0, $path);
+    $item = $this->addMenuLink('', $path);
 
-    $this->drupalGet('admin/structure/menu/item/' . $item['mlid'] . '/edit');
-    $this->assertFieldByName('link_path', $path, 'Path is found with scheme-relative URL.');
+    $this->drupalGet('admin/structure/menu/item/' . $item->id() . '/edit');
+    $this->assertFieldByName('link[0][uri]', $path, 'Path is found with scheme-relative URL.');
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Common/UrlTest.php b/core/modules/system/src/Tests/Common/UrlTest.php
index 2676b8b..fcfab0a 100644
--- a/core/modules/system/src/Tests/Common/UrlTest.php
+++ b/core/modules/system/src/Tests/Common/UrlTest.php
@@ -285,30 +285,30 @@ public function testSchemeRelativeUrls() {
 
     // Verify scheme-relative URL can contain a fragment.
     $url = $test_url . '#drupal';
-    $result = \Drupal::url($url);
+    $result = Url::fromUri($url)->toString();
     $this->assertEqual($url, $result, 'Scheme-relative URL with fragment works without a fragment in $options.');
 
     // Verify fragment can be overidden in an external URL.
     $url = $test_url . '#drupal';
     $fragment = $this->randomMachineName(10);
-    $result = \Drupal::url($url, array('fragment' => $fragment));
+    $result = Url::fromUri($url, ['fragment' => $fragment])->toString();
     $this->assertEqual($test_url . '#' . $fragment, $result, 'Scheme-relative URL fragment is overidden with a custom fragment in $options.');
 
     // Verify external URL can contain a query string.
     $url = $test_url . '?drupal=awesome';
-    $result = \Drupal::url($url);
+    $result = Url::fromUri($url)->toString();
     $this->assertEqual($url, $result, 'Scheme-relative URL with query string works without a query string in $options.');
 
     // Verify external URL can be extended with a query string.
     $url = $test_url;
-    $query = array($this->randomMachineName(5) => $this->randomMachineName(5));
-    $result = \Drupal::url($url, array('query' => $query));
+    $query = [$this->randomMachineName(5) => $this->randomMachineName(5)];
+    $result = Url::fromUri($url, ['query' => $query])->toString();
     $this->assertEqual($url . '?' . http_build_query($query, '', '&'), $result, 'Scheme-relative URL can be extended with a query string in $options.');
 
     // Verify query string can be extended in an external URL.
     $url = $test_url . '?drupal=awesome';
-    $query = array($this->randomMachineName(5) => $this->randomMachineName(5));
-    $result = \Drupal::url($url, array('query' => $query));
+    $query = [$this->randomMachineName(5) => $this->randomMachineName(5)];
+    $result = Url::fromUri($url, ['query' => $query])->toString();
     $this->assertEqual($url . '&' . http_build_query($query, '', '&'), $result, 'Scheme-relative URL query string can be extended with a custom query string in $options.');
   }
 
diff --git a/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php b/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php
index 6013810..04f3f5a 100644
--- a/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php
+++ b/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php
@@ -108,7 +108,7 @@ public function providerFromUri() {
    * @expectedException \InvalidArgumentException
    */
   public function testFromInvalidUri($uri) {
-    $url = Url::fromUri($uri);
+    Url::fromUri($uri);
   }
 
   /**
@@ -119,7 +119,6 @@ public function providerFromInvalidUri() {
       // Schemeless paths.
       ['test'],
       ['/test'],
-      ['//test'],
       // Schemeless path with a query string.
       ['foo?bar'],
       // Only a query string.