Kansas City Chiefs backers had already begun celebrating when quarterback Patrick Mahomes took his first of three kneeldowns in the closing moments of Super Bowl 54.

But those who held a Super Bowl betting ticket for Mahomes hitting the Over on rushing yards were singing a different tune, one that likely included a lot of cursing.

Mahomes lost 15 total yards on three kneeldowns as he looked to drain time of the clock between 49ers timeouts. One play later, Mahomes fired a fourth-down pass long and wide that ran out the clock and secured the Chiefs’ first title in 50 years.

The Over/Under betting for total rushing yards by Mahomes at kickoff was 36.5. It had opened at just 27.5, but the Over turned out to be one of the more-popular prop bets of the night, pushing it a full nine yards.

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He had 44 yards rushing entering the final possession, but finished with 29 yards after the three victory formation plays.

It will go down as one of the more epic bad beats in Super Bowl history — perhaps the biggest in terms of prop bets.

"That was close to a six-figure swing (in favor of the house)," Jeff Davis, director of trading for Caesars Sportsbook, told ESPN.

FanDuel reported it had received three times as many wagers on Mahomes’ rushing yards total than his passing yards total. William Hill said it was the biggest Super Bowl prop bet on its books.

One sportsbook, however, has decided that the outcome was so ridiculous, it’s giving back. PointsBet announced it would refund all bettors who took Mahomes Over 30.5 yards or more will be refunded their wager. FanDuel, DraftKings and other sportsbooks that have yet to announce any refund.