diff --git a/application/WarehouseCategory/WarehouseCategory.php b/application/WarehouseCategory/WarehouseCategory.php
index 129b19f18..46aeec39a 100644
--- a/application/WarehouseCategory/WarehouseCategory.php
+++ b/application/WarehouseCategory/WarehouseCategory.php
@@ -5,7 +5,7 @@ class WarehouseCategory extends TTCrudBaseModel {
     public string $description;
     public ?string $articleNumberPrefix;
     public int $create;
-    public int $create_by;
+    public ?int $create_by;
     public ?int $edit;
     public ?int $edit_by;
-}
\ No newline at end of file
+}