Livingston earned a deserved 2-1 win over Partick Thistle in the first leg of the Ladbrokes Premiership play-off final on Thursday night.
Kris Doolan gave the Jags an early lead in front of 5,469 fans at the Tony Macaroni Arena but Keaghan Jacobs quickly equalised for the home side.
David Hopkin's team were on top and got the winner 16 minutes from time when substitute Josh Mullin's cross was swept home by midfielder Scott Pittman.
Livingston are now just 90 minutes away from a second successive promotion, with the second leg at The Energy Check Stadium at Firhill on Sunday, live on BT Sport at 3.30pm.
