diff --git a/core/lib/Drupal/Core/Render/Element/MachineName.php b/core/lib/Drupal/Core/Render/Element/MachineName.php
index 8b9c840..d60d550 100644
--- a/core/lib/Drupal/Core/Render/Element/MachineName.php
+++ b/core/lib/Drupal/Core/Render/Element/MachineName.php
@@ -238,10 +238,10 @@ public static function validateMachineName(&$element, FormStateInterface $form_s
     // @see https://www.drupal.org/node/2557299.
     $needs_revalidation = $form_state->get('needs_revalidation', $element['#name']);
     if ($needs_revalidation) {
-      self::isUnique($element, $form_state);
+      static::isUnique($element, $form_state);
     }
     elseif ($element['#default_value'] !== $element['#value']) {
-      self::isUnique($element, $form_state);
+      static::isUnique($element, $form_state);
     }
 
   }