Sales Order to Purchase Order Link with Reservation still allowing Pick Lists to be Generated

In AX2009, we create a Sales Order and then create a linked Purchase Order for the items as we specifically need to ship the serial numbers to be received on the Purchase Order to the customer. We have Automatic Reservation turned on for the order and the application creates the correct reservation and shows the quantity in ‘Ordered Reserved’.

However, if there is any available inventory in stock, the system is allowing the warehouse to generate a Pick List for those items (prior to the linked purchase order being received).

Is there a setting I’m missing somewhere to not allow Pick List Generation / Registration until the linked PO is received?

Thanks for any insight