diff -u b/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php b/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php
--- b/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php
@@ -15,7 +15,7 @@
 /**
  * Adds tables and fields to the SQL entity query.
  */
-class Tables {
+class Tables implements TablesInterface {
 
   /**
    * @var \Drupal\Core\Database\Query\SelectInterface