diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/filter/String.php b/core/modules/views/lib/Drupal/views/Plugin/views/filter/String.php
index 1af32f0..90acd1b 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/filter/String.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/filter/String.php
@@ -21,7 +21,7 @@
 class String extends FilterPluginBase {
 
   // exposed filter options
-  var $always_multiple = TRUE;
+  protected $alwaysMultiple = TRUE;
 
   protected function defineOptions() {
     $options = parent::defineOptions();