diff --git a/core/includes/entity.api.php b/core/includes/entity.api.php
index f4d0e3d..7585ddb 100644
--- a/core/includes/entity.api.php
+++ b/core/includes/entity.api.php
@@ -66,6 +66,10 @@ function hook_entity_info_alter(&$entity_info) {
  */
 function hook_entity_create(\Drupal\Core\Entity\EntityInterface $entity) {
   if (!isset($entity->foo)) {
+    // @todo This example assumes that $entity is an instance of EntityNG, but
+    //   any object implementing EntityInterface will work here and in the
+    //   entity type specific version of this hook.
+    //   Remove this comment when merging Entity and EntityNG.
     $entity->foo->value = 'bar';
   }
 }