Chesterfield took a second half lead through Kristian Dennis after being set up by just-on sub Matt Briggs but Cambridge United then used the blustery conditions well to equalise direct from a free-kick, Jevani Brown with the leveller. Just eight minutes later Uche Ikpeazu won it for the home side, anticipating well to convert from close in.
After both teams won in midweek, unsurprisingly both managers selected unchanged teams meaning ex -Spireite Liam O'Neil was on the bench for Chesterfield's first visit to this ground since 2002.
Chris O'Grady didn't make the trip due to a back problem allowing Jordan Sinnott to return to the matchday squad.
With a blustery bit of Storm Brian at the backs of the blue kitted Spireites, George Maris beat the breeze to get in the game's first shot but Joe Anyon gathered with ease.
Jordan Flores was unlucky to see the ball nicked off his toe in the six yard box after Scott Wiseman and Andy Kellett combined to open up the U's rearguard. Kellett soon found himself behind the home back line again but his delivery in was scrambled clear as Chesterfield were spending plenty of time in the opposition's half.
Wiseman overlapped Kellett and delivered a teasing cross but keeper David Forde jumped high to get there ahead of Flores as Spireites continued to enjoy the majority of the ball.
Wiseman blocked a shot from Greg Taylor before Brad Halliday looped up a 17th minute ball that dropped into the net but referee Busby ruled the effort out for a foul on Anyon.
Spireites earned the first corner of the game, on the left, but Louis Reed's kick was cleared away. Jabo Ibehre fired over after Brown nicked the ball in midfield and put a perfectly weighted ball through for the striker who should have done better from 10 yards.
Flores teased out a right sided corner, he took the kick himself but the ball didn't beat the near post defender.
Robbie Weir had to leave the field to have a bloodied nose patched up at a point in the game where both sides were struggling to create chances with the wind beginning to play a real part in proceedings.
Kellett's cross was deflected for a corner after a rapid move from defence but an offside flag halted the short corner routine. Piers Mingoia's shot from the right corner of the box clipped a blue sock and went out for the home side's first corner that saw Brown shoot wide from a swivel shot, the last attacking call of the first half.
Brown used the wind to float in a free-kick that deceived Anyon and went out for a corner that was overhit and flew straight out for a Spireites throw which wasn't cleared and U's garnered another corner which Brown kicked straight out to ease the pressure.
Ian Evatt headed away another Brown free-kick as United sought to use the wind to their advantage, seeking to find the heads of their two six-foot-plus strikers, Anyon punched clear as another teaser was delivered into the box.
Briggs came on for Wiseman and the sub received from Flores, his first involvement, he dashed into the box and squared a perfect ball for Dennis to find the net from two yards for his 9th of the season.
Conor Dimaio replaced Kellett. Joe Rowley cut back for Reed to shoot, his 20 yard left footer deflected for a corner and Sam Hird headed Flores's corner but Forde caught the ball on the line.
Shaun Derry made a double substitution on 64 to try and boost his team and on 70 the hosts were level. Reed fouled Brown by the touchline on Cambridge's right, he was carded for the challenge. Brown took the kick himself and used the wind well, seeing the ball drift in just under the bar.
Rowley found Dennis but Spireites main marksman didn't find the power he wanted from the shot and his effort was blocked. Ikpeazu used his strength well but his shot passed the upright and the same player then anticipated the drop of the ball in the wind but this time hit too high.
Medy Elito hit high but United's pressure told when Brown's shot was well saved and Ikpeazu popped in the loose ball from close range. Anyon saved from Ikpeazu as the confident hosts stepped up a gear.
Spireites won a corner and used the initiative to stay in the final third for a while with Reed, Rowley and Dimaio all involved in solid play. Diego De Girolamo came on for Weir with time ticking away. Evatt was carded for a box-edge foul but Brown drifted this one far too high.
De Girolamo won a corner but United cleared as Chesterfield looked to grab a late leveller which looked on when Dennis gathered but Halliday made a fantastic tackle to nick the ball from the well positioned striker.
Four minutes of added time was signalled as United sought to keep the ball in the corner segment and their tactics worked well as Spireites were unable to find a way out of their own half until three and a half of those had been played and then Flores hit high with the game's final kick.
No midweek game, so it's Carlisle United at home next Saturday as Jack Lester seeks to guide his team to a first Proact win.
Cambridge: Forde, Halliday, Taylor, Legge, Carroll, Deegan, Maris (Dunk 64), Brown, Mingoia (Elito 64), Ikpeazu, Ibehre. Subs (not used): Mitov, Taft, O'Neil, Foy, Hawkins.
Goals: Brown 70, Ikpeazu 78
Chesterfield: Anyon, Barry, Evatt, Hird, Wiseman (Briggs 53), Weir (De Girolamo 82), Reed, Rowley, Kellett (Dimaio 58), Flores, Dennis. Subs (not used): Jones, Maguire, McCourt, Sinnott.
Goal: Dennis 55
Ref: John Busby (Oxfordshire)
Bookings: Reed, Evatt, Flores (Chesterfield)
Attendance: 4529 (422 from Chesterfield)