diff --git a/htdocs/core/class/commonobject.class.php b/htdocs/core/class/commonobject.class.php
index ef31fb50485..e65226b13d1 100644
--- a/htdocs/core/class/commonobject.class.php
+++ b/htdocs/core/class/commonobject.class.php
@@ -167,8 +167,9 @@ abstract class CommonObject
 	 * @var CommonObject To store a cloned copy of object before to edit it and keep track of old properties
 	 */
 	public $oldcopy;
+
 	/**
-	 * @var CommonObject To store old value of a modified ref
+	 * @var string To store old value of a modified ref
 	 */
 	public $oldref;