Thomas O'Ware scored the only goal as Morton won 1-0 away to Dumbarton in the Ladbrokes Championship on Tuesday night.
The victory means Jim Duffy's men are now four points clear of Dunfermline Athletic and Queen of the South in the final play-off spot.
Ryan Wallace converted two penalties to help Arbroath come from behind to beat Stranraer 4-1 at Stair Park and climb to third place in Ladbrokes League 1.
First-half substitute Russell McLean scored a hat-trick at Galabank but it wasn't enough to give Peterhead all three points as they were pegged back in a 3-3 draw with Annan Athletic.
Blair Henderson netted twice for Annan and Peter Watson grabbed a late leveller to leave Peterhead five points behind Ladbrokes League 2 leaders Montrose with a game in hand.
