diff --git a/schema/mysql-changes/upgrade_28.sql b/schema/mysql-changes/upgrade_28.sql
new file mode 100644
index 00000000..24513116
--- /dev/null
+++ b/schema/mysql-changes/upgrade_28.sql
@@ -0,0 +1 @@
+ALTER TABLE sync_rule MODIFY filter_expression TEXT DEFAULT NULL;
diff --git a/schema/mysql.sql b/schema/mysql.sql
index 152c5824..aab27db0 100644
--- a/schema/mysql.sql
+++ b/schema/mysql.sql
@@ -901,7 +901,7 @@ CREATE TABLE sync_rule (
   object_type ENUM('host', 'user') NOT NULL,
   update_policy ENUM('merge', 'override', 'ignore') NOT NULL,
   purge_existing ENUM('y', 'n') NOT NULL DEFAULT 'n',
-  filter_expression TEXT NOT NULL,
+  filter_expression TEXT DEFAULT NULL,
   PRIMARY KEY (id)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;