Accounting for security deposits

In one of my bank accounts there is a transaction that represents the security/key deposit I paid to my landlord for office space. Currently it is listed as a payment for "Office Costs". But is there a better way to deal with deposits? I'm expecting to get it back, so it's money owed by a debtor.

The new bills interface is very handy, and without wanting to introduce too much scope creep I was wondering whether it could be adapted to provide a means for representing money owed which does not relate to invoices - sort of a negative bill.