Linfield's lead at the top of the Premiership has been cut to three points after this surprise 1-0 defeat by Dungannon Swifts at Stangmore Park.
The Blues dominated the first half and Aaron Burns sent two efforts over the Swifts bar.
The only goal came against the run of play on 37 minutes, with a Jamie Douglas shot deflecting over keeper Jonathan Tuffey.
It is Linfield's first league defeat since the end of August.
Matt Hazley and Johnny Topley were involved in the build-up to the only goal, with Douglas seeing his deflection loop over Tuffey and into the Blues net.
Linfield defender BJ Burns was making his 200th appearance for the club but he was forced off with an injury in the first half.
The visitors failed to sustain consistent pressure in their search for an equaliser although Aaron Burns went close with a header.
Swifts keeper Niall Morgan made a number of fine saves while the central defensive pairing of Adam McMinn and Dermot McCaffrey kept the Blues attack at bay.
It's a first league win for Dungannon in eight games and takes them up to eighth, while Linfield have suffered a second loss this week after Tuesday's League Cup defeat by Crusaders.
"We're absolutely delighted with the three points and overall we deserved to win," said Swifts boss Darren Murphy.
"From start to finish the boys competed well and we got the rub of green, which has been missing in recent matches."