Bafetimbi Gomis scored the winner once again as Swansea City triumphed 2-1 to spoil Louis van Gaal's 50th match in charge of Manchester United.

The France international scored a somewhat fortuitous second when Swansea beat United by the same scoreline at the Liberty Stadium in February to complete a 2014-15 Premier League double over the Old Trafford outfit.

And it was the in-form Gomis, who now has nine goals from 10 top-flight matches, who settled matters in south Wales on Sunday, rounding off a Swansea turnaround in the 65th minute.

Juan Mata had put United in front early in the second half with his 50th goal in English football, before Andre Ayew headed Swansea level – the first time Van Gaal's men have conceded in the top flight this term.

Swansea's comeback was inspired by a tactical change from manager Garry Monk, who switched to a 4-3-1-2 formation moments before his side's leveller.

The result means Swansea have now won four of their last five fixtures against United, each by a 2-1 margin as the visitors were beaten for the first time this season..

Having picked up a thigh injury in training, the in-form Jefferson Montero was replaced by Wayne Routledge in the Swansea starting XI. United midfielder Ander Herrera was rewarded for his goal in a midweek UEFA Champions League victory over Club Brugge with a starting berth.

A nervy start from the home side saw United win a free-kick on the edge of the Swansea box in the opening couple of minutes, but goalkeeper Lukasz Fabianski got down well to keep out Memphis Depay's curling strike.

Mata then dragged a shot wide from close range when he found himself unmarked two minutes later, before Gomis snatched at Swansea's first chance to test Sergio Romero.

Swansea should have opened the scoring in the 25th minute when Jonjo Shelvey threaded a free-kick into the path of Gylfi Sigurdsson, who pulled his shot wide of the left-hand post.

Those chances sparked the beginning of a period of Swansea pressure as Shelvey tried his luck from long range when he spotted Romero off his line, before Gomis hit the left-hand post with a shot off the outside of his boot.

It was United who were in front three minutes into the second half when a Luke Shaw cross from the left found its way to Mata at the far post and the Spain international powered his finish into the roof of the net.

Fabianski then had to be alert when a Depay cross deflected off Ashley Williams and looked to be looping over his head – the Pole slapping the ball clear before denying Mata from close range.

Monk opted to bring Ki Sung-yueng on for Routledge after seeing his side fall behind and Sigurdsson soon found himself in acres of space on the right, crossing for Ayew to head down and beyond Romero for the equaliser.

The hosts were firmly in the ascendancy and Gomis put them in front five minutes later, tucking his shot under Romero after being played in by Ayew.

United made a trio of substitutions in a bid to salvage at least a point and Williams had to make a superb tackle to halt Wayne Rooney when he was clean through on goal late on.

There were no further chances for the visitors and Van Gaal's wait for a point against Swansea goes on.