diff --git a/Models/Issue.php b/Models/Issue.php
index cba4f13..522f9ac 100644
--- a/Models/Issue.php
+++ b/Models/Issue.php
@@ -62,7 +62,7 @@ class Issue
      * @var   int
      * @since 1.0.0
      */
-    private int $creator = null;
+    private ?int $creator = null;
 
     private static $instances = [];
 
diff --git a/Models/Message.php b/Models/Message.php
index d94143d..275e83d 100644
--- a/Models/Message.php
+++ b/Models/Message.php
@@ -55,7 +55,7 @@ class Message
      * @var   int
      * @since 1.0.0
      */
-    private int $creator = null;
+    private ?int $creator = null;
 
     private static $instances = [];