Derby celebrated a home win for only the second time this year as they beat Swansea 2-0 to move into the Championship play-off places.
Swansea had been the better side in the first half but they were undone by two corners after the break with Rhian Brewster and United States international Patrick Agyemang scoring the goals that gave the Rams a league double over the team from South Wales.
And County's first victory at Pride Park since New Year's Day moved them into sixth in the table.
The game began with Swansea almost paying the price for conceding a free-kick just outside the box when Agyemang was brought down in the 11th minute.
Joe Ward curled a low effort around the wall and the ball was heading for the bottom right corner until Lawrence Vigouroux plunged to his left to turn it behind.
The focus switched to the other end when Derby gave away a free-kick 25 yards out which Liam Cullen whipped just past Josh Vickers' left post.
Swansea were winning the ball too easily in midfield and Eom Ji-sung burst through on the right only to bend a shot wide with several teammates waiting for a cut back.
But despite getting into some threatening positions, the visitors had not forced Vickers into a save and Derby took advantage by scoring two minutes into the second half.
A shot was deflected behind for a corner and when Callum Elder swung the ball in, it was flicked on by Ben Brereton Diaz to Brewster who slammed a shot past Vigouroux after his initial header was blocked.
Derby took a big stride towards victory when Swansea were undone by another corner in the 67th minute.
Elder again provided an excellent delivery and Agyemang came in to rise above the defenders to score with a downward header.
Although Elder deserved credit for the corner, Swansea's marking was poor and it now looked a long way back for the Welshmen.
Gustavo Nunes had a chance to get them back in the game when he sprinted through on the left but his shot was too close to Vickers and Derby cleared the rebound.
Josh Tymon fired wildly off target from outside the box minutes later which summed up Swansea's afternoon in front of goal and Derby almost scored a third in the 84th minute.
Again it was a corner that caused panic in the visitors' defence with Agyemang again getting above everyone to power a header which Vigouroux palmed away.
The keeper rescued Swansea again with another good save to deny Jaydon Banel but by now the game was over as a contest.
Derby's John Eustace:
"It's something we spoke about before the game, about areas where we felt we could hurt them and when you're up against a really good team you have to find a way to score.
"The delivery was fantastic and the hard work that Matt Gardiner (assistant head coach) does day in day out to make sure we are prepared properly certainly comes out in games.
"It's a fantastic win. We had to find a way to win today against a really good footballing team and we knew we'd have to suffer at times without the ball.
"I thought in the first half the disconnection from the back to the front was a little bit too big when we tried to put pressure on the ball and we were a little bit loose when we did win it back.
"Obviously scoring when we did settled things down and I thought our shape was really good and we always looked a threat on transitions."
Swansea's Vitor Matos:
"When you concede a set-piece goal you can get frustrated with that of course but we knew that Derby were really dangerous from these situations.
"What was important for us was how we started the game and the performance we put on in the first half I thought was really good. We were dominant and aggressive and to do that here is not easy.
"Then the second half started with the goal from the set-piece and then we took a little bit of time to get back into the game.
"Slowly we got back and created again one of two situations but then a second goal from a set-piece and I think that changed a little bit the feeling inside.
"It's clear that we need to see it and analyse what happened and the first thing is to avoid set-pieces, that is the main thing."
