diff --git a/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php b/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php
index 1623b70..b662c3c 100644
--- a/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php
+++ b/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php
@@ -323,7 +323,7 @@ protected function getFieldDefinitions() {
       $entity_manager = \Drupal::entityManager();
       $entity_info = $entity_manager->getDefinition($this->targetEntityType);
       $definitions = array();
-      if (is_subclass_of($entity_info['class'], '\Drupal\Core\Entity\ContentEntityInterface')) {
+      if ($entity_info->isSubclassOf('\Drupal\Core\Entity\ContentEntityInterface')) {
         $entity = _field_create_entity_from_ids((object) array('entity_type' => $this->targetEntityType, 'bundle' => $this->bundle, 'entity_id' => NULL));
         foreach ($entity as $field_name => $items) {
           $definitions[$field_name] = $items->getFieldDefinition();