diff --git a/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/Field.php b/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/Field.php
index 2459a78..cab863b 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/Field.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/Field.php
@@ -215,6 +215,8 @@ public function __construct(array $values, $entity_type = 'field_entity') {
       throw new FieldException('Attempt to create a field with no type.');
     }
     // Temporary BC layer: accept both 'id' and 'field_name'.
+    // @todo $field_name and the handling for it will be removed in
+    //   http://drupal.org/node/1953408.
     if (empty($values['field_name']) && empty($values['id'])) {
       throw new FieldException('Attempt to create an unnamed field.');
     }