Purchase Order passed Funds Check incorrectly

Hi
I'm having an issue with a Purchase Order which was approved and reserved incorrectly because there were no funds available. When creating the invoice and matching to this PO, the invoice goes on hold with "no funds available" (which is correct). But I expect the PO not to be reserved when there are no funds available, this is, control funds at the PO level not only at the invoice level.

Is this a setup issue?

Thanks
Alicia