Peter MacDonald's second-half penalty proved to be the winner as Morton triumphed at home against Livingston in the First Division.
Michael Tidser's 25-yard short put the home side ahead after nine minutes.
But Iain Russell levelled from the penalty spot after Paul Di Giacomo hauled down Jason Talbot.
Morton re-established the lead nine minutes later when MacDonald converted from 12 yards after Tidser had been fouled by David Sinclair.
Stewart, McCann (Weatherson 68), Forsyth, Evans, McCaffrey, Tidser,Di Giacomo, Bachirou, MacDonald, Jackson (Campbell 65), O'Brien (McGeouch 69). Subs Not Used: Deans, Little.
Tidser 9, MacDonald 64 pen.
McNeil, Brown, Talbot, Sinclair (Boulding 79), Craig Barr, Watson, Fox, Keaghan Jacobs, Deuchar, Russell, Bobby Barr (Kyle Jacobs 84). Subs Not Used: Jamieson, McNulty, Travis.
Russell 55 pen.