Morton's eight-match unbeaten run came to an end with a 1-0 defeat at home to Hamilton.
The away side had won just once all season before kick-off but Steven May's first-half goal gave them the three points.
May collected Jonathon Routledge's pass in the 21st minute and fired in a low 20-yard drive into the bottom right-hand corner.
The visitors were denied a second by a fantastic save by Derek Gaston, after May had headed Alister Crawford's right-wing free-kick goalwards.
Morton pressed for an equaliser and Scott Taggart's fierce effort from the edge of the area forced Kevin Cuthbert into a good save.
As the game entered stoppage-time Michael Tidser was denied an equaliser as Cuthbert held his low shot from the edge of the area.