diff --git a/install/db/172-database.php b/install/db/172-database.php
new file mode 100644
index 000000000..9c7146e33
--- /dev/null
+++ b/install/db/172-database.php
@@ -0,0 +1,20 @@
+<?php
+// +-----------------------------------------------------------------------+
+// | This file is part of Piwigo.                                          |
+// |                                                                       |
+// | For copyright and license information, please view the COPYING.txt    |
+// | file that was distributed with this source code.                      |
+// +-----------------------------------------------------------------------+
+
+if (!defined('PHPWG_ROOT_PATH'))
+{
+  die('Hacking attempt!');
+}
+
+$upgrade_description = 'reduce sessions.id length to 50 chars';
+
+$query = 'ALTER TABLE `'.PREFIX_TABLE.'sessions` CHANGE `id` `id` varchar(50) binary NOT NULL default \'\';';
+pwg_query($query);
+
+echo "\n".$upgrade_description."\n";
+?>
diff --git a/install/piwigo_structure-mysql.sql b/install/piwigo_structure-mysql.sql
index ebd7a5898..664f0836e 100644
--- a/install/piwigo_structure-mysql.sql
+++ b/install/piwigo_structure-mysql.sql
@@ -334,7 +334,7 @@ CREATE TABLE `piwigo_search` (
 
 DROP TABLE IF EXISTS `piwigo_sessions`;
 CREATE TABLE `piwigo_sessions` (
-  `id` varchar(255) binary NOT NULL default '',
+  `id` varchar(50) binary NOT NULL default '',
   `data` mediumtext NOT NULL,
   `expiration` datetime NOT NULL default '1970-01-01 00:00:00',
   PRIMARY KEY  (`id`)