Andrew Jackson's strike was the difference as Morton claimed their first win in five league matches with a victory over Dundee.
Allan Moore's men claimed an identical result the last time these two sides met at Dens Park in August, although their Boxing Day triumph was largely helped by goalkeeper Dominic Cervi's penalty save from Matthew Lockwood.
After Cervi kept out long-range efforts from both Jake Hyde and Gavin Rae, Jackson gave the Ton a 22nd-minute lead after tapping in from Archie Campbell's cross.
Morton's defence were largely doing a superb job of repelling Dundee's attacks although the pressure eventually told as Thomas O'Ware fouled Gary Irvine in the area six minutes after the interval.
Lockwood's placed penalty, however, was comfortably caught by Cervi and although Dundee continued to push forward, they failed to create any meaningful opportunities.
Dundee: Douglas, Irvine, Lockwood, McGregor, Weston (McKeown 84), Riley, Chisholm (Bayne 87), Rae, Conroy, Hyde, Milne (Elliot 60).Subs Not Used: Gibson,McCluskey.
Booked: Chisholm, Riley, Weston, Elliot.
Morton: Cervi, Evans, O'Ware, Graham, Smyth, McGeouch, Tidser (Derek Young 89), Bachirou, O'Brien, Jackson (MacDonald 69), Campbell (Weatherson 59).Subs Not Used: Stewart, Di Giacomo.
Booked: O'Ware, MacDonald.
Goals: Jackson 22.
Ref: John Beaton