Hull City missed a chance to climb to the top of the Championship as Jon Toral's first-half strike proved enough to earn Birmingham City a 1-0 win at St Andrew's.
Toral has had to make do with a place on the bench in Birmingham's last two matches but marked his return to the starting XI by getting one over former Blues boss Steve Bruce.
The Tigers remain one point adrift of league leaders Burnley, while Birmingham close in on the play-off positions.
Hull started brightly and threatened through Moses Odubajo in the opening stages, but the winger was unable to direct his volley goalwards from a Robert Snodgrass cross.
And it was Birmingham who made the breakthrough thanks to Toral after 14 minutes - his wonderful turn on the edge of the box earning the luck that came with a heavy deflection as the ball made its way into the back of the net.
For all Hull's possession, they were unable to level before the break - Jake Livermore and Michael Dawson hitting the woodwork, while Abel Hernandez saw appeals for a penalty against a Paul Robinson handball turned down.
Clayton Donaldson almost doubled the advantage with an eye-catching overhead kick, but Birmingham were indebted to goalkeeper Tomasz Kuszczak as they saw out the victory.
The former Manchester United stopper was forced into an impressive double save in the second half to keep out Snodgrass and Sam Clucas, ensuring a sixth win in seven home league matches for the hosts.