An injury-time header from Stuart Beavon denied MK Dons the Buckinghamshire spoils over rivals Wycombe Wanderers and ensured Karl Robinson's men left Adams Park with only a point.
Jay O'Shea missed a penalty in the 10th minute of the game but when Daniel Powell rounded 'keeper Nikki Bull early in the second half it looked as though the points would be heading back to Milton Keynes.
However, Wycombe, who are battling against the drop, kept going right until the last minute and when Gareth Ainsworth's corner was whipped in it was Beavon who applied the sucker-punch with a powerful header.
Stephen Gleeson was welcomed back into the starting 11 after serving a three-match ban and Alan Smith also returned after missing out in the midweek win over Leyton Orient through injury.
The Wanderers side included Anthony McNamee, who was released by the Dons in January after a disappointing spell with the men from MK, and he had an early touch on the ball before Marvin McCoy lashed a shot wide of David Martin's post inside the first minute.
Daniel Powell showed the physical attributes in the opening phases in his defensive duties and also in his attacking mode when he hassled the ball off Grant Basey and crossed to Smith. The midfielder was inside the box as he tried to tuck a volley into the back of the net, unfortunately he miss-judged his effort and skied this shot over the bar.
Smith's movement in the box appeared to be causing the Chairboys' defence some problems and when McCoy brought him down inside the 10th minute referee Jock Waugh pointed to the penalty spot. With Dean Bowditch, the regular penalty taker, on the bench it was Jay O'Shea who stepped up and tried to place the ball to Nikki Bull's right. Unfortunately the spot-kick lacked the power needed and Bull was able to smother the ball at the post.
The Dons were then presented with a free-kick on the left touchline which was taken by O'Shea, but he failed to beat the first defender. The ball, however, found its way to Gleeson who, from the best part of 40-yards, fired a brilliant effort which moved through the air only to dip just over the bar.
Despite playing in sweltering condition, the game had a lively pace to it as both sides recognised the importance three points would have on their respective aims for the season.
Wycombe looked panicky at the back but when going forward they always carried threat, as demonstrated when Stuart Beavon drilled a first-time low shot through the Dons' box and, after an initial spill, Martin was able to take control before Ben Strevens could tap-in.
Mathias Kouo-Doumbe showed excellent desire to prevent Wycombe from taking the lead on the half-hour mark when he threw his bodies in the way of a fierce drive by Basey to deny the defender from what seemed like a certain goal.
Typical to a derby, there were a number of disruptions to the game with play pausing for the referee to intervene and add some calmness into proceedings as strong challenges were made by both teams.
A lapse in concentration almost proved very costly for the Dons when a long boot up field by Bull was excellently flicked over the visitors' backline and released Beavon into space. The forward only had Martin to beat but he wasted a golden opportunity as he fizzed his shot wide.
The half-time team talk seemed to deliver the inspiration the Dons needed when, just two minutes into the second half, a fine through ball from Darren Potter found MacDonald on the edge of the box and the striker noted the movement of Powell who was in a better position and unselfishly sprayed the ball to his feet.
Powell demonstrated great composure as he knocked the ball around 'keeper Powell to spark energetic celebrations from the away fans behind the goal.
Seconds later Powell found himself back in space when O'Shea broke down the left but on this occasion Bull made a great block. Wycombe were stunned by the blistering pace the Dons were showing and when the ball dropped to Kouo-Doumbe at the left of the Chairboys' goal the defender showed great technique to strike a fine right-footed volley inches over.
Desperate to find a way back into the game Wycombe began to shoot-on-sight but when Stuart Lewis tried to find an equaliser from distance it was a comfortable save for Martin, while Basey wasted a great opportunity to cause some problems with a free-kick on the right as he sent his delivery over without ever looking likely to cause Martin any problems.
With Wycombe still possessing the ability to threaten the scoresheet the Dons strengthened their own attacking options with both Dean Bowditch and Jabo Ibehre brought on from the bench.
The Chairboys had Gareth Ainsworth to turn to whenever the chance to deliver set plays into the box came their way and, as the clock ticked down, the experienced winger whipped in a dangerous cross into the Dons' six-yard box but Doherty, who was excellent in defence for Wycombe, nodded over.
At the other end Powell was yet again the Dons' danger man in front of goal when he skipped across the challenges in the penalty area yet his shot fell inches wide.
There was late drama at Adams Park though when Wycombe keeper Bull went forward for a corner in the 90th minute and Beavon rose highest to plant a header into the net and clinch a late point for the home side.
Wycombe Wanderers (4-3-3): Bull (c); McCoy, Laing, Doherty, Basey; Lewis, Eastmond, Hackett (Ainsworth 64); Strevens, Beavon, McNamee (McClure 61).
Subs not used: Stewart, Scowen, Dunne.
Booked: Basey, Lewis
MK Dons (4-2-3-1): Martin; Kouo-Doumbe, Flanagan, Williams, Lewington (c); Gleeson, Potter; Powell, Smith (Ibehre 78), O'Shea (Bowditch 64); MacDonald (Chadwick 90).
Subs not used: McLoughlin, Hall.
Referee: Jock Waugh