diff --git a/broker/migrate/mysql/V7__alter_device_token.sql b/broker/migrate/mysql/V7__alter_device_token.sql
new file mode 100755
index 00000000..6192d61c
--- /dev/null
+++ b/broker/migrate/mysql/V7__alter_device_token.sql
@@ -0,0 +1 @@
+ALTER TABLE t_user_session MODIFY _token VARCHAR(240) DEFAULT NULL;