Reverse an Invoice Adjustment (Write Back) in AR R12

I have an invoice that was Written Off via an adjustment following non-payment and exhausting all recovery means.

The customer has now been located and payments can be collected.

I need to reverse the Write Off Adjustment to reinstate to value of the original invoice.

I've created a "Write Back" adjustment, with the same details as the original Write Off; and trying to add this as a reversing line on:

Account Details > Adjust

But, I get an error that states an adjustment must make the transactions Zero. I kinda get that but, is there a way of 'unadjusting' an invoice, without creating another transaction??