diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/filter/FilterPluginBase.php b/core/modules/views/lib/Drupal/views/Plugin/views/filter/FilterPluginBase.php
index ad10227..11a7444 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/filter/FilterPluginBase.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/filter/FilterPluginBase.php
@@ -311,7 +311,7 @@ public function operatorSubmit($form, &$form_state) { }
   /**
    * Shortcut to display the value form.
    */
-  function showValueForm(&$form, &$form_state) {
+  protected function showValueForm(&$form, &$form_state) {
     $this->valueForm($form, $form_state);
     if (empty($this->no_operator)) {
       $form['value']['#prefix'] = '<div class="views-group-box views-right-70">' . (isset($form['value']['#prefix']) ? $form['value']['#prefix'] : '');