Billionaire Stewart Rahr may regret not signing a prenup, as he could be on the hook for an $800 million payment to his wife, who’s filing for divorce after 43 years of marriage.

Getting half of his $1.6 billion fortune would be New York’s biggest divorce payouts of all-time.

To be fair, the wife doesn’t seem to be a gold-digger, as she married Stewart before he had any money.

Still … $800 million is a big chunk of money that she didn’t actually earn herself.