Error reconciling bank statement with negative balance

[Nick Prater <..hidden..>]

I am trying to reconcile a credit card account via Cash->Reconciliation.

On this month's statement, the credit card company owe me money. I 
therefore wish to enter a negative amount in the 'Statement Balance' field.

If I try to do this, an error is generated:

Error!
Invalid statement balance. Hint: Try entering a number

Am I doing something stupid, or is this a bug? I'd appreciate a second 
opinion!

If it's a bug, I'm happy to work on a fix and report back.

Best wishes,

Nick