Purchase Order Processing - Blanket Orders

When creating a PO from a blanket order, how should you handle the payment terms?  I find if the supplier in the blanket order is different from the supplier used in the actual PO and they have different payment terms, the terms default to the original supplier on the blanket order when processing the Invoice through AP.  Any suggestions on what we need to do to stop this from happening?   We currently use JDE World A9.2.1