diff --git a/Models/Survey.php b/Models/Survey.php
index 03d03b9..df785fb 100644
--- a/Models/Survey.php
+++ b/Models/Survey.php
@@ -63,7 +63,7 @@ class Survey
      * @var   int
      * @since 1.0.0
      */
-    private int $creator = null;
+    private ?int $creator = null;
 
     private static $instances = [];