diff --git a/plugins/calendar/drivers/kolab/SQL/mysql.initial.sql b/plugins/calendar/drivers/kolab/SQL/mysql.initial.sql
index de339260..d5009616 100644
--- a/plugins/calendar/drivers/kolab/SQL/mysql.initial.sql
+++ b/plugins/calendar/drivers/kolab/SQL/mysql.initial.sql
@@ -11,7 +11,7 @@ CREATE TABLE IF NOT EXISTS `kolab_alarms` (
   `user_id` int(10) UNSIGNED NOT NULL,
   `notifyat` DATETIME DEFAULT NULL,
   `dismissed` TINYINT(3) UNSIGNED NOT NULL DEFAULT '0',
-  PRIMARY KEY(`alarm_id`),
+  PRIMARY KEY(`alarm_id`,`user_id`),
   CONSTRAINT `fk_kolab_alarms_user_id` FOREIGN KEY (`user_id`)
     REFERENCES `users`(`user_id`) ON DELETE CASCADE ON UPDATE CASCADE
 ) /*!40000 ENGINE=INNODB */;
diff --git a/plugins/calendar/drivers/kolab/SQL/mysql/2014082600.sql b/plugins/calendar/drivers/kolab/SQL/mysql/2014082600.sql
new file mode 100644
index 00000000..501eb5ce
--- /dev/null
+++ b/plugins/calendar/drivers/kolab/SQL/mysql/2014082600.sql
@@ -0,0 +1,2 @@
+ALTER TABLE `kolab_alarms` DROP PRIMARY KEY;
+ALTER TABLE `kolab_alarms` ADD PRIMARY KEY (`alarm_id`, `user_id`);