Ademola Lookman scored his first Leicester goal as they beat Millwall in the Carabao Cup third round.
He pounced from eight yards out after Kelechi Iheanacho's 20-yard shot had been parried by keeper George Long, Leicester's first shots on target.
Iheanacho sealed the win as he ran on to a ball down the right wing, cut in and curled home.
Brendan Rodgers' Foxes host fellow Premier League side Brighton in the fourth round.
Millwall had several chances in Wednesday's defeat with Ryan Leonard missing, Connor Mahoney forcing a save and Ben Thompson heading over.
Both sides made plenty of changes from their weekend fixtures, and Leicester were well below their best in the first half.
The free-kick Youri Tielemans sent over the bar was their only effort of the first half.
There were just two saves in the whole game - Danny Ward stopping Mahoney's effort and Long's parry that led to the opening goal.
Leicester assistant manager Chris Davies: "Ade [Lookman] has been outstanding since he came in, with his training and mentality. That's been a real highlight, and he got his rewards today.
"It was a game of few chances so we had to work hard for the chances we got. It was great for Ade to get the goal.
"Kele scored an excellent goal, he set up the first one and then scored with a great strike. His all-round play was really good and it was a goalscoring performance, which is always good for a striker."
Millwall boss Gary Rowett: "When you go toe to toe with a very good Premier League side, you can't make mistakes.
"We gave the ball away and allowed them into a scoring position and they are sometimes the moments that cost you. But I thought we competed really well tonight."