diff --git a/htdocs/resource/class/dolresource.class.php b/htdocs/resource/class/dolresource.class.php
index d7ef8cf14e1..0dcf23a9ffb 100644
--- a/htdocs/resource/class/dolresource.class.php
+++ b/htdocs/resource/class/dolresource.class.php
@@ -61,6 +61,9 @@ class Dolresource extends CommonObject
 
 	public $cache_code_type_resource = array();
 
+	/**
+	 * @var Dolresource Clone of object before changing it
+	 */
 	public $oldcopy;
 
 	/**