A Dean Marshall strike gave Sligo Rovers their first victory in the Setanta Sports Cup at Solitude on Saturday afternoon.
The defeat means the Belfast side are pointless after two games, while Sligo move on to four points in the Group One table.
Liam Boyce put the hosts in front after nine minutes, but a close-range header from Rob Turner had the visitors level after 24.
A cool finish by the same player six minutes before the break gave Paul Cook’s side the half-time advantage.
Jason Bannon levelled matters on 67, but Sligo were not to be denied and Marshall’s volleyed effort with a quarter of an hour to go sent their enthusiastic fans home happy.