Dundee fought back with three second-half goals to overcome Morton at Dens Park.
The Dee had the ball in the back of the net seven minutes in, but Nicky Riley's effort was ruled out for offside.
The visitors took the lead after 22 minutes when Dougie Imrie's corner found Tomas Peciar in the middle of the box and the Slovakian powered a header into the top-left corner.
Dundee equalised a minute after the restart when Peter MacDonald slotted home from the middle of the six-yard box.
MacDonald then gave them the lead after 49 minutes, smashing Riley's cross past keeper Nicolas Caraux.
Craig Beattie sealed victory for Dundee after 70 minutes, sweeping home the rebound from Riley's effort.
Dundee: Letheren, Irvine, Gallacher, Iain Davidson, Dyer, Riley (McBride 88), McAlister, Rae, Conroy, MacDonald (Doris 88), Beattie (Monti 74).
Subs Not Used: Lockwood, Benedictus, Boyle, Twardzik.
Goals: MacDonald 47, 50, Beattie 71.
Morton: Caraux, Taggart, Page, Peciar, Fitzpatrick, Michal Habai (Stirling 70), Bachirou, Wallace, Fulton, Imrie, Campbell (McNeil 76).
Subs Not Used: Gaston, Mark McLaughlin, Verlaque, Knight.
Goals: Peciar 23.
Ref: Iain Brines