diff --git a/calendar/setup/tables_update.inc.php b/calendar/setup/tables_update.inc.php
index ba725b0391..24284d601f 100644
--- a/calendar/setup/tables_update.inc.php
+++ b/calendar/setup/tables_update.inc.php
@@ -668,7 +668,7 @@
 				'fd' => array(
 					'cal_id' => array('type' => 'auto', 'nullable' => False),
 					'owner' => array('type' => 'int', 'precision' => 8, 'nullable' => False),
-					'category' => array('type' => 'int', 'precision' => 8, 'default' => '0', 'nullable' => False),
+					'category' => array('type' => 'int', 'precision' => 8, 'default' => '0', 'nullable' => True),
 					'groups' => array('type' => 'varchar', 'precision' => 255, 'nullable' => True),
 					'datetime' => array('type' => 'int', 'precision' => 8, 'nullable' => True),
 					'mdatetime' => array('type' => 'int', 'precision' => 8, 'nullable' => True),