diff --git a/core/modules/views/lib/Drupal/views/ViewsDataHelper.php b/core/modules/views/lib/Drupal/views/ViewsDataHelper.php
index 6185ebf..feb249f 100644
--- a/core/modules/views/lib/Drupal/views/ViewsDataHelper.php
+++ b/core/modules/views/lib/Drupal/views/ViewsDataHelper.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\views;
 
+use Drupal\Component\Utility\Unicode;
+
 /**
  * Defines a helper class for stuff related to views data.
  */
@@ -167,14 +169,14 @@ public function fetchFields($base, $type, $grouping = FALSE, $sub_type = NULL) {
    *   decided.
    */
   protected static function fetchedFieldSort($a, $b) {
-    $a_group = drupal_strtolower($a['group']);
-    $b_group = drupal_strtolower($b['group']);
+    $a_group = Unicode::strtolower($a['group']);
+    $b_group = Unicode::strtolower($b['group']);
     if ($a_group != $b_group) {
       return $a_group < $b_group ? -1 : 1;
     }
 
-    $a_title = drupal_strtolower($a['title']);
-    $b_title = drupal_strtolower($b['title']);
+    $a_title = Unicode::strtolower($a['title']);
+    $b_title = Unicode::strtolower($b['title']);
     if ($a_title != $b_title) {
       return $a_title < $b_title ? -1 : 1;
     }