The Kansas City Chiefs and the Denver Broncos played themselves on heck of a football game on Monday night, with the Chiefs storming back in the fourth quarter, scoring a late touchdown to win 27-23.

Much of the praise has been deservedly given to sensational young quarterback Patrick Mahomes, who threw for 304-yards and one touchdown, and scoring a rushing touchdown of his own. He was routinely calm under pressure, scrambling from the pocket to make to huge completions — including using his wrong hand to throw a short pass at one point. However, during the game-winning drive, one of his biggest plays on the night probably shouldn’t have counted.

On a 3rd & 7 from midfield, Mahomes connected with Kareem Hunt on a 35-yard pass. It was a clutch first down and a huge gain in yards. But a closer look at the play clock shows that it expired before the snap, meaning the Chiefs should have been hit with a Delay of Game penalty, turning the 3rd & 7 into a 3rd & 12.

Here’s a clip of the snap, with the game clock in the background:

The Broncos had just under two minutes to come back with a touchdown of their own, but ultimately came up short when they tried a hook and ladder gadget play on fourth down with 16 seconds left.

After the game, Broncos linebacker Brandon Marshall said that the refs told his team they had simply “missed it.”

It’s entirely possible that Mahomes and the Chiefs would have found a way to score even if the penalty had been called correctly. After all, they are undefeated for a reason. Still, it’s proven hard enough to beat the Chiefs so far this season without them getting a bit of extra help from a distracted ref.