diff --git a/htdocs/core/class/commonobject.class.php b/htdocs/core/class/commonobject.class.php
index e872e56adf5..786b3e9959d 100644
--- a/htdocs/core/class/commonobject.class.php
+++ b/htdocs/core/class/commonobject.class.php
@@ -168,6 +168,8 @@ abstract class CommonObject
 	 */
 	public $oldcopy;
 
+	public $oldref;
+
 	/**
 	 * @var string		Column name of the ref field.
 	 */