Kelechi Iheanacho became the first player in English football to score a goal after VAR intervention as Leicester beat Fleetwood 2-0 to book their place in the fourth round of the FA Cup.
The Leicester striker initially saw his second strike of the night ruled out for offside, but the decision was checked by the Video Assistant Referee as referee Jon Moss overturned a tight call to award the goal.
Earlier, Iheanacho broke the deadlock for his side in the 43rd minute before the historic VAR moment secured Leicester victory and a fourth-round tie away at Peterborough.
Mahrez was one of two players to keep their place in the Leicester side from Saturday's 0-0 draw with Chelsea, and the Algeria international, who was captain for the evening, looked to make an early impact, releasing Daniel Amartey but the full-back's cross was easily cut out by goalkeeper Chris Neal.
Leicester: Jakupovic (7), Amartey (7), Dragovic (6), Benalouane (6), Fuchs (6), Iborra (7), Silva (7), Mahrez (8), Gray (7), Iheanacho (8), Slimani (6).
Subs: Albroghton (7), Vardy (6), Okazaki (6).
Fleetwood: Neal (7), Bell (6), Pond (7), Hiwula (6), Dempsey (6), McAleny (7), Bolger (7), Glendon (6), Jones (6), Hunter (6), Schwabl (6).
Subs: Burns (6), Grant (6), Cole (6).
Man of the match: Khelechi Iheanacho
Leicester were not having things all their own way against the League One side and Eldin Jakupovic was forced into smart saves to deny Conor McAleny and Kyle Dempsey.
In the 33rd minute, Mahrez grazed the outside of the post but it wasn't long before Leicester had the lead with Islam Slimani flicking the ball on for Iheanacho, who slid the ball under the onrushing Neal.
It was not only Leicester's first shot on target of the evening, but the Premier League club's first of the entire tie including the goalless draw at Highbury 10 days ago.
Leicester made nine changes from the side that drew 0-0 against Chelsea with Riyad Mahrez, who was named captain, one of the two players to keep his place. Fleetwood made just three changes with Gethin Jones, George Glendon and Jordie Hiwula-Mayifuila all coming into the starting line-up.
Slimani might have extended the lead at the start of the second half but he snatched at his chance and put the ball wide.
Iheanacho twice had the ball in the net during the second half. His first effort was rightly ruled out but on the second occasion after 77 minutes, after the flag again went up but Moss consulted with the video assistant referee, and after a pause of one minute and seven seconds it was 2-0 to Leicester.
Jamie Vardy came on as a substitute against his former club with 10 minutes remaining, bringing applause from both sets of supporters as Leicester comfortably saw out the tie to progress to the next round.
Man of the Match
Iheanacho's second goal of the night will go down in the history books with the striker becoming the first player in English football to score a goal via a VAR decision.
In the end, it was quite a comfortable night for Claude Puel's side but only after the intervention of VAR. Iheanacho was the beneficiary and it capped an excellent night for the former Manchester City striker, who scored his second and third goals for the club.
Leicester City have won 17 of their last 19 FA Cup home games against lower league opposition (D1 L1), winning each of their last six at the King Power.
Iheanacho has scored seven goals in eight appearances in the FA Cup, however these were his first goals as a Leicester player (five for Manchester City).
Leicester are back in Premier League action on Saturday with a home game against Watford, while Fleetwood also return to league action against Blackburn in League One.