Liam Boyce's second-half strike earned Hearts a hard-fought 1-0 victory away to Livingston in the Scottish Premiership.
The Northern Irishman scored his 11th goal of the season to turn the game in the Jambos' favour following a first half in which they were reliant on goalkeeper Craig Gordon to keep them on level terms.
The win took third-placed Hearts five points clear of both Dundee United and Motherwell.
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Livingston made four changes to the side that lost 2-0 at Aberdeen on Wednesday as Ayo Obileye, Bruce Anderson, Odin Bailey and the suspended Jackson Longridge dropped out to be replaced by James Penrice, Andrew Shinnie, Jack McMillan and Craig Sibbald.
There were two alterations to the Hearts team that started the 1-0 defeat at Celtic Park on Thursday as Alex Cochrane and Boyce came in for Peter Haring and Josh Ginnelly, with manager Robbie Neilson reverting to his favoured 3-4-3
formation.
Livingston had the first chance in the fourth minute when Alan Forrest got himself clear on the left after McMillan had dispossessed Ben Woodburn just outside the Hearts box, but the attacker dragged his low shot well wide from 12 yards.
A minute later, home midfielder Stephane Omeonga shot straight at Gordon from the edge of the box.
Hearts were forced into a change in the 14th minute as Michael Smith suffered a blow to the back and had to be replaced by Taylor Moore.
The visitors had a huge escape in the 24th minute when Livingston had four consecutive attempts on goal, three of which were saved by Gordon.
Shinnie's initial shot from inside the box was brilliantly blocked by the Scotland goalkeeper, Sibbald fired the rebound against the post, then Gordon tipped Jason Holt's follow-up shot on to the post before the 38-year-old picked himself up to thwart Shinnie again.
Hearts were struggling to get a foothold and Neilson took decisive action in the 28th minute when he replaced Woodburn with Haring and switched to 4-2-3-1.
The change helped the visitors steady the ship and they went ahead four minutes after the break when Barrie McKay took a pass from John Souttar and played a first-time ball into the path of striker Boyce who darted into the box and blasted past the exposed Max Stryjek.
The visitors threatened again in the 57th minute when Aaron McEneff saw a shot from edge of the box tipped behind by Stryjek before McKay had a goal ruled out for offside shortly afterwards.
Livingston tried to muster a response and Forrest saw a shot blocked by Gordon in the 61st minute before McEneff and McKay both spurned great chances to double Hearts' lead in quick succession.
What the managers said...
Livingston manager David Martindale: "When your striker is going through on goal in the 90th minute and they get it wrong you cannot defend that.
"I genuinely feel hard done by and I'm not one to normally have a go at officials. I have told him he is on by two yards and the linesman tells me that it is not his fault we got beat.
"I can see his point but that decision did play a part in the defeat. If he had said he would look back at it and say 'sorry' if he got it wrong, that would be fine. But don't be arrogant to me.
"It is poor because you are not allowed to speak to officials. I don't like doing this but we have been done by another decision against us."
Hearts boss Robbie Neilson: "A game of four quarters! I thought we started well in the first five, 10 minutes. We had a couple of half-chances, but then the game became very scrappy.
"We had no control in the middle and they were picking up all the second balls. It was only when we brought Peter on that we got a bit of stability and that allowed us to grow into the game.
"We had a couple of chances to put it to bed and didn't manage to do it, and at 1-0 it was a wee bit edgy towards the end of the game, but we defended well."
Asked about his first-half substitution, Neilson said: "You need to do it at times. You can't wait until half-time - sometimes you just need to do it. Thankfully it paid off."
What's next?
Livingston host Hibs on Wednesday night (7.45pm), while Heats hist champions Rangers on Sunday December 12 (12pm) in a game you can see live on Sky Sports Football.