Index: trunk/roundcubemail/program/include/session.inc
===================================================================
--- trunk/roundcubemail/program/include/session.inc	(revision 1685)
+++ trunk/roundcubemail/program/include/session.inc	(revision 1823)
@@ -185,5 +185,6 @@
 
   setcookie(session_name(), '', time() - 3600);
-  setcookie(session_name(), $random, $lifetime, $cookie['path'], $cookie['domain']);
+  setcookie(session_name(), $random, $lifetime, $cookie['path'], $cookie['domain'],
+            $_SERVER['HTTPS'] && ($_SERVER['HTTPS']!='off'));
 
   return true;