Morton's eight-match unbeaten run came to an end with a home defeat to Hamilton Accies.
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 a low 20-yard drive into the bottom right-hand corner.
Accies 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.
Morton: Gaston, Taggart, Rutkiewicz, Mark McLaughlin, Dyer, Wallace (Graham 65), Wilkie (Hardie 59), Tidser, O'Brien, Weatherson, Campbell. Subs Not Used: Hutton, Reid, Naismith.
Booked: Wallace, Campbell.
Hamilton: Cuthbert, Gordon, Canning, Page, McGlinchey, Devlin, Finnie (Gillespie 89), Crawford, Routledge, Longridge (Ryan 82), May. Subs Not Used: Christie, Fraser, Keatings.
Booked: Canning, Gillespie.
Goals: May 21.
Ref: Paul Robertson