diff --git a/Admin/Install/db.json b/Admin/Install/db.json
index 9d20694..f934ac2 100644
--- a/Admin/Install/db.json
+++ b/Admin/Install/db.json
@@ -37,7 +37,7 @@
             "exchange_version": {
                 "name": "exchange_version",
                 "type": "VARCHAR(50)",
-                "null": null
+                "null": false
             }
         }
     }
diff --git a/Models/InterfaceManagerMapper.php b/Models/InterfaceManagerMapper.php
index 7a5d959..5d130fa 100644
--- a/Models/InterfaceManagerMapper.php
+++ b/Models/InterfaceManagerMapper.php
@@ -51,14 +51,6 @@ final class InterfaceManagerMapper extends DataMapperAbstract
      */
     protected static $table = 'exchange';
 
-    /**
-     * Created at.
-     *
-     * @var string
-     * @since 1.0.0
-     */
-    protected static $createdAt = 'exchange_created_at';
-
     /**
      * Primary field name.
      *