diff --git a/htdocs/core/class/commonobject.class.php b/htdocs/core/class/commonobject.class.php
index 6340facf31a..2fc6d22fd62 100644
--- a/htdocs/core/class/commonobject.class.php
+++ b/htdocs/core/class/commonobject.class.php
@@ -1223,7 +1223,7 @@ abstract class CommonObject
      *	@param	int			$id			To force other object id (should not be used)
      *	@param	string		$format		Data format ('text', 'date'). 'text' is used if not defined
      *	@param	string		$id_field	To force rowid field name. 'rowid' is used if not defined
-     *	@param	User|string	$user		Update last update fields also if user object provided
+     *	@param	User|string	$user		Update last update fields also if user object provided. If not provided, current user is used.
      *  @param  string      $trigkey    Trigger key to run (in most cases something like 'XXX_MODIFY')
      *	@return	int						<0 if KO, >0 if OK
      */
@@ -1247,7 +1247,7 @@ abstract class CommonObject
         if ($format == 'text') $sql.= $field." = '".$this->db->escape($value)."'";
         else if ($format == 'int') $sql.= $field." = ".$this->db->escape($value);
         else if ($format == 'date') $sql.= $field." = ".($value ? "'".$this->db->idate($value)."'" : "null");
-        if (is_object($user)) $sql.=", fk_user_modif = ".$user->id;
+        if (empty($user) && is_object($user)) $sql.=", fk_user_modif = ".$user->id;
         $sql.= " WHERE ".$id_field." = ".$id;
 
         dol_syslog(get_class($this)."::".__FUNCTION__."", LOG_DEBUG);