Leaders Birmingham suffered a first League One defeat in 19 games as play-off chasing Bolton came from behind to beat the Blues 3-1 at the Toughsheet Community Stadium.
The visitors were in position for a customary victory when Emil Hansson scored his first league goal to put Birmingham in front after 23 minutes.
But six minutes before half-time Wanderers hit back against the run of play.
John McAtee’s low shot beat Bailey Peacock-Farrell at his near post for the striker’s fourth goal in as many games.
He also had another effort disallowed for offside before half-time.
City had not conceded a goal in their five previous league outings. But a first third-tier defeat since November 23 was confirmed in the second half as Wanderers turned on the style to boost their play-off hopes.
Skipper George Thomason nipped in to nudge Steven Schumacher’s side in front after 49 minutes.
And top scorer Aaron Collins netted his 16th goal from substitute Joel Randall’s assist to seal the points in the 71st minute.
