City were beaten for the first time in six matches as Aden Flint’s own goal gifted struggling visitors Sheffield United maximum points at Ashton Gate.
The unfortunate defender sliced a low cross high into his own net 13 minutes from time to decide the outcome of a contest short on chances from start to finish.
Skipper Sam Baldock had the Robins’ best – one in the first half and one in the second – but saw his first effort saved and blazed the second over the crossbar amidst strong claims for a City penalty.
Referee Keith Stroud did little to make friends with the home crowd by disallowing an untidy equaliser on the stroke of added time as the hosts’ unbeaten run came to an abrupt end.
Sean O’Driscoll made two changes to the side who started the 1-1 draw at Tranmere last time out, with Scott Wagstaff replacing the injured Bobby Reid on the right flank and Marvin Elliott stepping into the centre to add some extra physicality at the expense of Simon Gillett.
It was a slow burner of a first half, with City enjoying the majority of the early possession without converting the lion’s share into chances.
Instead the visitors were the first to threaten when defender Harry Maguire got his head to Simon Lappin’s free kick but looped his effort over the crossbar.
At the other end, a clumsy Maguire lunge earned him the first booking of the afternoon before Jay Emmanuel-Thomas dragged the resulting free kick wide of goal.
City’s top scorer would have a better chance on 25 minutes when Baldock squeezed between two challenges only to be hauled down on the edge of the penalty area, but handed free kick duty to Nicky Shorey whose kick was comfortably held by Blades keeper George Long.
It was turning into a set-piece trade off. Emmanuel-Thomas’ barge into the back of Lappin presented an opening for Tony McMahon, but his dead ball was easily kept at bay by the stooping Elliott Parish.
The crowd would have to wait until the 37th minute for a first notable opportunity from open play. Emmanuel-Thomas’ clever pass released Baldock bearing down on goal, but his shot was blocked by the legs of Long with Wagstaff waiting in vain to his right.
A difficult watch was hardly improving after the interval, with the exception of a couple of speculative shots from distance from United pair Conor Coady and Lyle Taylor.
Any form of a breakthrough looked unlikely and O’Driscoll responded by tweaking the formation.
Derrick Williams, back from international duty with Republic of Ireland Under-21s, replaced Shorey as City reverted to a back three with Greg Cunningham and Wagstaff employed as wing-backs for the final quarter of the game.
But it was another set-piece which threatened to unlock the visitors. Emmanuel-Thomas’ corner found its way through to Elliott, whose shot appeared to strike a hand inside the box before Baldock’s shot on the turn cleared the crossbar.
The Blades had offered very little as an attacking force, only for a stroke of luck to tilt the balance in their favour 13 minutes from time.
McMahon’s surge on the overlap found him in a promising crossing position, firing a low ball across the six-yard box which Flint could only slice into his own net at the near post.
It was harsh on the hosts, who, despite struggling to create, had never looked like surrendering their clean sheet.
O’Driscoll’s last card after bringing Stephen McLaughlin off the bench was to introduce Marlon Harewood as a supplementary striker for the final ten minutes.
But when City thought they had snatched a late equaliser, Stroud ruled it out for an infringement on Long after the keeper had dropped a high ball from virtually on his own goal line.