Inventory Source Flag on ePro Requisition line

When creating an ePro Requisition for inventory Items using catalogs, the 'Inventory Source Flag' gets selected as Y (checked) for all inventory items. However, the client requirement is to have this unchecked. The client wants all of the requisitions created to get sourced to Purchase Order. Is there a configuration to turn the automatic defaulting of this flag on requisitions? We are implementing 9.2 and we are om PUM 23. Will appreciate any help.