Glentoran's six-match unbeaten run in the Irish Premiership ended when they were surprisingly beaten 3-2 at home by Dungannon Swifts on Tuesday night.
The Glens took an early lead when Andrew Waterworth beat a defender to get a touch on Jason Hill's shot.
James Costello flicked in an equaliser and then Michael McKerr edged the Swifts in front in the 39th minute.
Costello's curling shot made it 3-1 midway through the second half with David Howland heading in for the Glens.
The result is a boost for two-from-bottom Dungannon who had suffered recent defeats at the hands of Ballinamallard and Coleraine.
But it is a setback for Eddie Patterson's Glentoran who had been hoping to move within two points of third-placed rivals Linfield.
Things had been looking good for the Glens when Waterworth scored his 20th goal of the season in the sixth minute.
Hill made a strong run down the left and shot past the advancing keeper Johnny Curran with Waterworth getting the final touch.
Waterworth had another chance when put through by Richard Clarke but on this occasion the shot was saved by Curran.
Costello equalised in the 28th minute, flicking in with his foot at the near post from former Glens player Neal Gawley's corner.
Defender McKerr then surged forward to the edge of the box and his shot looped off keeper Morris and into the net to put the Swifts 2-1 up.
In the 64th minute Costello went through and beat Morris with a nicely curling shot past the advancing Morris and into the top corner.
Howland pulled one back in the 86th minute, heading in from Stephen Carson's left-wing cross.
The Glens pushed forward for a last-gasp equaliser with Colin Nixon sending an stoppage-time attempt wide.