diff --git a/lib/bastion-host-patch-manager.ts b/lib/bastion-host-patch-manager.ts
index f21ab9c..bea798f 100644
--- a/lib/bastion-host-patch-manager.ts
+++ b/lib/bastion-host-patch-manager.ts
@@ -33,7 +33,7 @@ export class BastionHostPatchManager extends Construct {
       allowUnassociatedTargets: false,
       cutoff: 0,
       duration: 2,
-      schedule: 'cron(0 3 * * SUN *)',
+      schedule: 'cron(0 3 ? * SUN *)',
     });
 
     const maintenanceTarget = new CfnMaintenanceWindowTarget(this, 'MaintenanceWindowTarget', {