diff --git a/core/modules/node/lib/Drupal/node/Plugin/views/argument_validator/Node.php b/core/modules/node/lib/Drupal/node/Plugin/views/argument_validator/Node.php
index 275a8f0..0234629 100644
--- a/core/modules/node/lib/Drupal/node/Plugin/views/argument_validator/Node.php
+++ b/core/modules/node/lib/Drupal/node/Plugin/views/argument_validator/Node.php
@@ -80,7 +80,7 @@ public function submitOptionsForm(&$form, &$form_state, &$options = array()) {
     $options['types'] = array_filter($options['types']);
   }
 
-  function validateArgument($argument) {
+  public function validateArgument($argument) {
     $types = $this->options['types'];
 
     switch ($this->options['nid_type']) {
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/views/argument_validator/Term.php b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/views/argument_validator/Term.php
index 76f0b36..7491199 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/views/argument_validator/Term.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/views/argument_validator/Term.php
@@ -93,7 +93,7 @@ public function submitOptionsForm(&$form, &$form_state, &$options = array()) {
     $options['vids'] = array_filter($options['vids']);
   }
 
-  function validateArgument($argument) {
+  public function validateArgument($argument) {
     $vocabularies = array_filter($this->options['vids']);
     $type = $this->options['type'];
     $transform = $this->options['transform'];
diff --git a/core/modules/user/lib/Drupal/user/Plugin/views/argument_validator/User.php b/core/modules/user/lib/Drupal/user/Plugin/views/argument_validator/User.php
index a6a64a2..764efde 100644
--- a/core/modules/user/lib/Drupal/user/Plugin/views/argument_validator/User.php
+++ b/core/modules/user/lib/Drupal/user/Plugin/views/argument_validator/User.php
@@ -72,7 +72,7 @@ public function submitOptionsForm(&$form, &$form_state, &$options = array()) {
     $options['roles'] = array_filter($options['roles']);
   }
 
-  function validateArgument($argument) {
+  public function validateArgument($argument) {
     $type = $this->options['type'];
     // is_numeric() can return false positives, so we ensure it's an integer.
     // However, is_integer() will always fail, since $argument is a string.
diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php
index 297703d..af7f12c 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php
@@ -80,7 +80,7 @@ protected function checkAccess(&$form, $option_name) {
     }
   }
 
-  function validateArgument($arg) { return TRUE; }
+  public function validateArgument($arg) { return TRUE; }
 
   /**
    * Process the summary arguments for displaying.
diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/None.php b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/None.php
index 1ef3667..c8aa8eb 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/None.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/None.php
@@ -22,7 +22,7 @@
  */
 class None extends ArgumentValidatorPluginBase {
 
-  function validateArgument($argument) {
+  public function validateArgument($argument) {
     if (!empty($this->argument->options['must_not_be'])) {
       return !isset($argument);
     }
diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Numeric.php b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Numeric.php
index ee53f64..05b7845 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Numeric.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Numeric.php
@@ -22,7 +22,7 @@
  */
 class Numeric extends ArgumentValidatorPluginBase {
 
-  function validateArgument($argument) {
+  public function validateArgument($argument) {
     return is_numeric($argument);
   }
 
diff --git a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Php.php b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Php.php
index 82c1f65..138a1df 100644
--- a/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Php.php
+++ b/core/modules/views/lib/Drupal/views/Plugin/views/argument_validator/Php.php
@@ -49,7 +49,7 @@ public function access() {
     return user_access('use PHP for settings');
   }
 
-  function validateArgument($argument) {
+  public function validateArgument($argument) {
     // set up variables to make it easier to reference during the argument.
     $view = &$this->view;
     $handler = &$this->argument;