diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 2bff21f..8214090 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -1852,7 +1852,7 @@ function hook_file_download($uri) {
  *   shipped file.
  */
 function hook_file_url_alter(&$uri) {
-  global $user;
+  $user = \Drupal::currentUser();
 
   // User 1 will always see the local file in this example.
   if ($user->id() == 1) {
@@ -2719,8 +2719,7 @@ function hook_url_outbound_alter(&$path, &$options, $original_path) {
 
   // Instead of pointing to user/[uid]/edit, point to user/me/edit.
   if (preg_match('|^user/([0-9]*)/edit(/.*)?|', $path, $matches)) {
-    global $user;
-    if ($user->id() == $matches[1]) {
+    if (\Drupal::currentUser()->id() == $matches[1]) {
       $path = 'user/me/edit' . $matches[2];
     }
   }
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 40c3234..e1bf500 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -123,8 +123,7 @@ function system_help($path, $arg) {
       }
       break;
     case 'admin/config/development/maintenance':
-      global $user;
-      if ($user->id() == 1) {
+      if (\Drupal::currentUser()->id() == 1) {
         return '<p>' . t('Use maintenance mode when making major updates, particularly if the updates could disrupt visitors or the update process. Examples include upgrading, importing or exporting content, modifying a theme, modifying content types, and making backups.') . '</p>';
       }
       break;
@@ -2188,7 +2187,7 @@ function system_user_login($account) {
  * Add the time zone field to the user edit and register forms.
  */
 function system_user_timezone(&$form, &$form_state) {
-  global $user;
+  $user = \Drupal::currentUser();
 
   $account = $form_state['controller']->getEntity();
   $form['timezone'] = array(