diff --git a/workflow/engine/data/mysql/schema.sql b/workflow/engine/data/mysql/schema.sql
index 4089c926a..dd3610b76 100644
--- a/workflow/engine/data/mysql/schema.sql
+++ b/workflow/engine/data/mysql/schema.sql
@@ -1001,7 +1001,7 @@ CREATE TABLE `EVENT`
 	`EVN_STATUS` VARCHAR(16) default 'OPEN' NOT NULL,
 	`EVN_WHEN_OCCURS` VARCHAR(32) default 'SINGLE',
 	`EVN_RELATED_TO` VARCHAR(16) default 'SINGLE',
-	`TAS_UID` VARCHAR(32) default '' NOT NULL,
+	`TAS_UID` VARCHAR(32) default '',
 	`EVN_TAS_UID_FROM` VARCHAR(32) default '',
 	`EVN_TAS_UID_TO` VARCHAR(32) default '',
 	`EVN_TAS_ESTIMATED_DURATION` DOUBLE default 0,