diff --git a/core/modules/comment/lib/Drupal/comment/Plugin/field/field_type/CommentItem.php b/core/modules/comment/lib/Drupal/comment/Plugin/field/field_type/CommentItem.php
index c24c608..c7222c2 100644
--- a/core/modules/comment/lib/Drupal/comment/Plugin/field/field_type/CommentItem.php
+++ b/core/modules/comment/lib/Drupal/comment/Plugin/field/field_type/CommentItem.php
@@ -81,8 +81,9 @@ public static function schema(FieldInterface $field) {
   public function instanceSettingsForm(array $form, array &$form_state) {
     $element = array();
 
-    $settings = $this->getInstance()->settings;
-    $field = $this->getInstance()->getField();
+    $instance = $this->getFieldDefinition();
+    $settings = $instance->settings;
+    $field = $instance->getField();
 
     $element['comment'] = array(
       '#type' => 'details',