diff --git a/install/mods-for-hesk/sql/installSql.php b/install/mods-for-hesk/sql/installSql.php
index 16d47086..a628dade 100644
--- a/install/mods-for-hesk/sql/installSql.php
+++ b/install/mods-for-hesk/sql/installSql.php
@@ -777,6 +777,7 @@ function execute260Scripts()
     executeQuery("INSERT INTO `" . hesk_dbEscape($hesk_settings['db_pfix']) . "settings` (`Key`, `Value`) VALUES ('enable_calendar', '1')");
     executeQuery("INSERT INTO `" . hesk_dbEscape($hesk_settings['db_pfix']) . "settings` (`Key`, `Value`) VALUES ('first_day_of_week', '0')");
     executeQuery("INSERT INTO `" . hesk_dbEscape($hesk_settings['db_pfix']) . "settings` (`Key`, `Value`) VALUES ('default_calendar_view', 'month')");
+    executeQuery("ALTER TABLE `" . hesk_dbEscape($hesk_settings['db_pfix']) . "settings` ADD PRIMARY KEY ( `Key` )");
 
     updateVersion('2.6.0');
 }
\ No newline at end of file