Floyd Mayweather stands to earn at least £77.6million for fighting and beating Conor McGregor in Las Vegas last month.
That figure could rise as high as £271m, but the American tried to make even more money out of the fight by betting on himself.
Mayweather left one sportsbook in a bad mood though, after his attempts to place the wager were delayed.
According to ESPN, Mayweather approached a sports betting vendor in Las Vegas around 3.30pm – just hours before the main event – and tried to stake around £310,000 on the fight ending inside 9.5 rounds.
The odds were 1/2, meaning the 40-year-old would have stood win make a £155,000 profit, but the bet was not placed.
Concerns over the legality of a fighter betting on anything other than a straight win reportedly caused a delay.
He then tried to bet on himself to win by knockout but was again frustrated by the delay and left without staking any money.
One source told ESPN: ‘He was p*ssed.’
Mayweather went on to beat McGregor courtesy of a stoppage one minute and five seconds into round 10.