diff --git a/htdocs/public/opensurvey/studs.php b/htdocs/public/opensurvey/studs.php
index 1d2d6d2d1e6..f522bc0ac14 100644
--- a/htdocs/public/opensurvey/studs.php
+++ b/htdocs/public/opensurvey/studs.php
@@ -1,6 +1,6 @@
 <?php
-/* Copyright (C) 2013      Laurent Destailleur <eldy@users.sourceforge.net>
- * Copyright (C) 2014 Marcos García				<marcosgdf@gmail.com>
+/* Copyright (C) 2013-2015 Laurent Destailleur <eldy@users.sourceforge.net>
+ * Copyright (C) 2014      Marcos García       <marcosgdf@gmail.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -46,7 +46,7 @@ if ($result <= 0) dol_print_error('','Failed to get survey id '.$numsondage);
 $nblignes=$object->fetch_lines();
 
 //If the survey has not yet finished, then it can be modified
-$canbemodified = ($object->date_fin > dol_now());
+$canbemodified = (empty($object->date_fin) || $object->date_fin > dol_now());
 
 
 /*