Penalty king Paul Caddis came up trumps again to earn Blues a tremendous win over fellow play-off hopefuls Cardiff City.
The spot-kick award itself was fortuitous as the ball struck the face rather than the arms of visiting defender Matthew Connolly during the final stages of the opening period.
Caddis fired low past David Marshall and it proved enough to claim the spoils in a game that took a time to get going but was full of action in the second-half.
Gary Rowett’s men rode their luck after the break but came on strong in the latter stages and could have made the victory more comprehensive.
Rowett made two changes from the side that drew at Preston. Shane Lowry came in for his debut at left-back in place of the injured Jonathan Grounds, whilst Jon Toral was favoured ahead of Andy Shinnie in the attacking midfield role.
Cardiff loanee Tony Watt’s clever chip into the area caused an early dangerous moment inside the Blues six-yard box, but Anthony Pilkington chose to try and head the ball back rather than go for goal and Michael Morrison cleared.
The visitors were then forced into an early change, Sean Morrison unable to continue after being tackled heavily but fairly by James Vaughan and Bruno Ecuele Manga took his place in the heart of the Cardiff defence.
The substitute came close to making a dramatic impact when he was inches away from connecting to an in-swinging free-kick.
At the opposite end, Demarai Gray flashed a shot well over whilst Stephen Gleeson’s swung in a terrific cross from the right that was veering towards the head of Vaughan but Manga diverted the ball behind.
Cardiff threatened again when Sammy Ameobi arrowed a cross from the right flank to Kenwyne Jones only six yards out, however Lowry got a vital touch that put the striker off and his weak header was easily claimed by Tomasz Kuszczak.
Blues also had to make a first-half substitution as Neal Eardley hobbled out of the action, but there was a ready-made replacement on the bench in Caddis.
The Scot made a vital early contribution by blocking Pilkington’s 25-yard shot, diverting the ball over the bar when the effort could have troubled Kuszczak.
Just after the half hour mark an in-swinging Gleeson corner caused problems for Cardiff, the ball bouncing menacingly across the six-yard box where Jonathan Spector looked well positioned to take advantage but tumbled over after a tangle of legs.
Blues continued to improve as the half went on, Gray producing a terrific cross which was met by Toral but the Spaniard couldn’t make a full connection and his glancing header drifted out towards the far corner.
Kuszczak was called upon to make a save low down to the left after Ameobi cut inside from the right but the winger failed to get much power into his shot.
Blues were given a golden chance to go in front in first-half stoppage-time, in rather controversial circumstances.
Cardiff keeper Marshall got into a mess when coming out to collect a cross, colliding with his own man Manga.
The ball dropped to Michael Morrison, who floated the ball back to Vaughan. The loanee’s shot was then blocked by what the referee felt was the hands of Connolly and the official pointed to the penalty spot.
However, TV replays showed that the ball had struck the Cardiff player firmly in the face. The visitors were understandably aggrieved.
After a long delay, Caddis kept his cool to convert his fourth spot-kick of the season and give Blues an interval advantage.
Four minutes into the second-half and Blues carved out a great opportunity to extend their lead.
Jacques Maghoma showed great persistence to harry and dispossess Lee Peltier and set up an attack on the edge of the box.
The winger was then in the right place to latch onto Vaughan’s pass and in turn set up Toral with a shooting chance 10 yards out to the right of the goal.
The Arsenal loanee got plenty of power into his shot but it was at a comfortable height for the keeper and Marshall was able to tip the ball around the post.
Cardiff came close to drawing level when Scott Malone’s low cross landed at Pilkington’s feet but the winger screwed his shot wide.
And even better chance arrived moments later when Ameobi found himself in space on the right of the area but he got his attempted curler horribly wrong and sent the ball well wide of the far post.
The visitors were getting in the ascendancy and Rowett responded by making his second change of the night, David Davis replacing Toral in the centre of the park.
But the Blues defence stood firm, repelling wave after wave of Cardiff attacks with some brave and determined blocks and headers.
A final swap from the hosts saw the departure of Lowry, who put in a solid display in his first Blues appearance, replaced by Greg Halford.
Rowett’s men were still looking to break away at every opportunity and grab that second goal; Gray had a chance of getting it but crashed his shot over from the left side of the six-yard box.
Davis also had a chance seven minutes from time when Gray’s blocked shot fell into his path but from wide on the left the midfielder miscued his driven effort across the area.
It was now Blues creating the openings and Gray was next to try his luck from the right flank but his fierce shot was palmed out by Marshall.
Cardiff’s last real chance came and went as Kuszczak turned aside Malone’s shot and Blues saw out the win to move up one place to seventh in the Sky Bet Championship table.