OXFORD United's excellent festive form continued as Peter Leven's penalty was enough to beat high-flying Cheltenham Town.
Chris Wilder's men had shown some classy touches in beating Exeter City and AFC Wimbledon over Christmas, but this victory owed plenty to guts and determination.
Leven took his chance from the spot in the first half after Tom Craddock had been tripped, which put United in charge.
They had chances, particularly in the second half, to make the game safe, but with only a slender lead the defence had to work hard to keep Cheltenham out.
Jake Wright stood out in an excellent rearguard action which sealed a fourth straight win and extended their unbeaten run into double figures.
United made just one change to the starting line-up, with Michael Duberry named in the XI for the first time this season.
He came in for Michael Raynes, who dropped out of the squad altogether.
With the U's in good form and Cheltenham going into the game in the automatic promotion places, the game promised much.
But there was little fluent football in the first half, with both sides visibly struggling to get to grips with a difficult surface which was feeling the after-effects of the wet weather and Saturday's rugby match.
Alfie Potter picked up where he left off in Saturday's 3-0 win at AFC Wimbledon, stinging the palms of Robins goalkeeper Scott Brown with the first sight of goal early on.
There was little to choose between the sides, but United found a breakthrough on 16 minutes.
Sean Rigg slipped a ball into Craddock, whose heels were clipped by Sido Jombati in the area.
Leven, who had scored from the spot in both previous games against Cheltenham this season, had no problems beating Brown from 12 yards.
The next clear chance came midway through the half.
United fans prepared to let out an enormous cheer as Duberry collected Rigg's cross, but the veteran could only shoot wide amid an audible sigh of disappointment from the terraces.
Cheltenham's lofty position in the table owed much to an excellent home record and they again struggled to find top gear on their travels.
Mark Yates's side had plenty of possession before the break, but struggled to open up their hosts.
Jermaine McGlashan was their main threat, but the winger could not stretch U's goalkeeper Ryan Clarke with his best chance on 25 minutes after getting the better of Damian Batt.
Jake Wright made several important interceptions to snuff out promising attacks, while Luke O'Brien did well at left back.
At the other end United only threatened fleetingly. Their best opening for a second goal before the break came on 34 minutes, when Brown just beat Rigg to a Constable through ball.
United came closest to scoring early in the second half.
Constable latched on to a loose ball and set Potter free down the right. The winger's cross sparked panic in Cheltenham's defence, but they scrambled the ball to safety.
The visitors went on to enjoy a good spell, pinning United back for several minutes.
A host of crosses rained down on Clarke's penalty area, but again Town could not forge a clear chance.
As they pushed forward in search of an equaliser, spaces began to open up.
Midway through the half Potter engineered a chance for himself, beating his man in the box but he placed a shot wide.
Substitute Josh Parker came close shortly after coming on. The new signing did well to cut in from the flank, only to blaze wildly over.
The lack of a second goal made United vulnerable and they rode their luck at times.
Substitute Shaun Harrad fizzed a shot from range just over and Billy Jones curled a free-kick wide in quick succession.
It ensured a nail-biting climax and hearts were in mouths in stoppage time when the ball fell to McGlashan, but the winger steered a shot over under pressure from Clarke.
But United deserved their clean sheet and saw out time to claim a hard-fought victory.