diff --git a/htdocs/product/inventory/class/inventory.class.php b/htdocs/product/inventory/class/inventory.class.php
index ecb9df3a40c..fb255364470 100644
--- a/htdocs/product/inventory/class/inventory.class.php
+++ b/htdocs/product/inventory/class/inventory.class.php
@@ -141,7 +141,7 @@ class Inventory extends CommonObject
 	public $fk_product;
 
 	/**
-	 * @var int Categories id
+	 * @var string Categories id separated by comma
 	 */
 	public $fk_categories_product;