Receiving AAI for G/L Class Code Invalid during Voucher Match

The PC AAI for the company and supplier G/L Class Code does not exist (PCxxxx) although the default PC____ does.  This is probably a one-time use supplier for this company and I would prefer not to do a temporary change to the G/L Class on the Supplier Master or temporarily add an AAI to support.  Is it possible to change the G/L Class on the transaction and if so where do I go to do this?