"assign as payment" - 2 splits

[tereque]

the new "assign as payment' function is a great new feature. I just have 
one problem now and I wonder whether there is a way to solve it nicely.

    # I have 2 open invoices to a customer
    # I have 1 payment that covers the total sum of these 2 payments

When I use 'assign' as payment to the second split, the first is being 
disconnected from its corresponding invoice. Any way to do this?