diff --git a/htdocs/core/modules/modMargin.class.php b/htdocs/core/modules/modMargin.class.php
index 2aa81102fa8..b2bc41220c3 100644
--- a/htdocs/core/modules/modMargin.class.php
+++ b/htdocs/core/modules/modMargin.class.php
@@ -77,7 +77,11 @@ class modMargin extends DolibarrModules
 		$this->langfiles = array("margins");
 
 		// Constants
-		$this->const = array();			// List of particular constants to add when module is enabled
+		// List of particular constants to add when module is enabled (key, 'chaine', value, desc, visible, 'current' or 'allentities', deleteonunactive)
+		// Example: $this->const=array(0=>array('MYMODULE_MYNEWCONST1','chaine','myvalue','This is a constant to add',1),
+		//                             1=>array('MYMODULE_MYNEWCONST2','chaine','myvalue','This is another constant to add',0, 'current', 1)
+		// );
+		$this->const = array(0=>array('MARGIN_TYPE','chaine','1','Rule for margin calculation by default',0,'current',0));			// List of particular constants to add when module is enabled
 
 		// New pages on tabs
 		$this->tabs = array(