diff --git a/install-dev/upgrade/php/ps1600_add_missing_index.php b/install-dev/upgrade/php/ps1600_add_missing_index.php
new file mode 100644
index 000000000..61072742f
--- /dev/null
+++ b/install-dev/upgrade/php/ps1600_add_missing_index.php
@@ -0,0 +1,36 @@
+<?php
+/*
+* 2007-2013 PrestaShop
+*
+* NOTICE OF LICENSE
+*
+* This source file is subject to the Open Software License (OSL 3.0)
+* that is bundled with this package in the file LICENSE.txt.
+* It is also available through the world-wide-web at this URL:
+* http://opensource.org/licenses/osl-3.0.php
+* If you did not receive a copy of the license and are unable to
+* obtain it through the world-wide-web, please send an email
+* to license@prestashop.com so we can send you a copy immediately.
+*
+* DISCLAIMER
+*
+* Do not edit or add to this file if you wish to upgrade PrestaShop to newer
+* versions in the future. If you wish to customize PrestaShop for your
+* needs please refer to http://www.prestashop.com for more information.
+*
+*  @author PrestaShop SA <contact@prestashop.com>
+*  @copyright  2007-2013 PrestaShop SA
+*  @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
+*  International Registered Trademark & Property of PrestaShop SA
+*/
+
+function ps1600_add_missing_index()
+{
+	$key_exists = Db::getInstance()->executeS('
+	SHOW INDEX
+	FROM `'._DB_PREFIX_.'connections`
+	WHERE Key_name = "id_guest"');
+	if (!$key_exists)
+		Db::getInstance()->execute('ALTER TABLE `'._DB_PREFIX_.'connections` ADD INDEX (`id_guest`)');
+	return true;
+}
diff --git a/install-dev/upgrade/sql/1.6.0.1.sql b/install-dev/upgrade/sql/1.6.0.1.sql
index fa32d2424..fec326595 100644
--- a/install-dev/upgrade/sql/1.6.0.1.sql
+++ b/install-dev/upgrade/sql/1.6.0.1.sql
@@ -27,3 +27,5 @@ CREATE TABLE `PREFIX_configuration_kpi_lang` (
   `date_upd` datetime default NULL,
   PRIMARY KEY (`id_configuration_kpi`,`id_lang`)
 ) ENGINE=ENGINE_TYPE DEFAULT CHARSET=utf8;
+
+/* PHP:ps1600_add_missing_index(); */;