Ghana captain Andre Ayew scored his second goal of the season for his Swansea City but was powerless as they succumbed to the first defeat of the season.
Huddersfield Town inflicted a 2-1 defeat on Steve Cooper's men at their own backyard at the Liberty Stadium.
It is their first defeat of the 2020/2021 Championship season after failing to a Harry Toffolo's first half strike.
Swansea equalised through Andre Ayew who netted his second goal of the campaign from the penalty spot.
Carlos Corberan's team lost their opening two games of the campaign without scoring a goal, but caused problems for a Swansea defence starting life without Joe Rodon.
Andre Ayew equalised from the penalty spot after Korey Smith was fouled, but it Huddersfield delivered a winner in a more even second half which featured chances at both ends.
Koroma, 21, guided the ball home from the edge of the penalty area to give Huddersfield a first away win of the campaign and seven points from their last three games.
Swansea, for whom this was a first defeat in eight regular-season outings stretching back to 11 July, will feel they should have got something.