Airdrie handed leaders Raith Rovers only their second defeat of the cinch Championship campaign as they recorded a 1-0 home win.
Nikolay Todorov went close to opening the scoring in the 17th minute but was denied by a fine save from visiting goalkeeper Andrew McNeil.
Todorov managed to break the deadlock seven minutes later, heading in from Mason Hancock’s cross to put Airdrie ahead.
Rovers, who had Ross Millen sent off late on, were unable to find an equaliser as they slumped to defeat in the league for the first time since losing to the same opponents in September.