Processing a MIGO for a reservation

I have a question regarding the goods issue against a reservation:-

Let me explain the scenario:-

A person was processing the goods issue against a particular reservation and he hadn't posted it yet when another person started processing a goods issue for the same reservation. System let both of them process the goods issue for the same exact reservation.

I ran this scenario and it looks like it wasn't any fluke thing and indeed the system would let two users process the same reservation if neither is posted.

Is there a way to stop it?