The on-loan Rangers winger suffered a red face when he failed to convert a spot-kick during St Johnstone's Scottish Cup final triumph over Hibs last month.
However, he has now banged in two in the space of four days for Scot Gemmill's young guns. His penalty in Wednesday's clash with the same opponents at Dumbarton's C&G Stadium was not enough to prevent a 2-1 loss, but he ensured Gemmill's boys claimed a morale-boosting win ahead of September's European Championship qualifiers with the late winner from 12 yards.
Tom Clayton and Ben Williamson had earlier twice put Scotland ahead, only for Northern Ireland to counter with efforts from Ben Wylie and Ryan Waide.
Gemmill rang the changes to the side beaten in midweek, with Jack Burroughs one of four players to keep his starting slot for the second leg of this friendly doubleheader.
It was just as well the Coventry right-back was up to speed as his last-ditch tackle denied Sean Stewart an early opener for the visitors after Archie Mair failed to hold Oisin Smyth's strike.
Northern Ireland goalkeeper Dermott Mee hardly looked assured either. He was robbed by Daniel Mackay as he went walkabout outside his box, but the new Hibs winger failed to take advantage of the empty net.
Visiting boss Andy Crosby could not believe what he was watching when Mee again miskicked the ball straight at Mackay for a second time. At least on this occasion the Manchester United youngster was up sharp to make a vital block.
There was nothing he could do as Scotland went ahead after 23 minutes as Mackay's corner broke loose at the near post, allowing Clayton to stab home from close range.
The lead lasted just five minutes, however. Celtic youngster Wylie looked suspiciously offside as he burst straight through the middle of the Scotland defence. He got lucky again when the ball span back to him from Burroughs' tackle before smashing home.
Gemmill's boys regained the lead just in time for the half-time team talks, with Williamson arcing a sublime finish in off the crossbar from 25 yards out.
Mee continued to cause panic in the Northern Ireland back line as the second half got under way.
A mix-up with Aaron Donnelly saw him again stranded off his line but Mackay wasted his third big chance by lobbing over.
It was a Scotland blunder which saw the scores levelled up again after 72 minutes.
Inverness' Robbie Deas had only been on the pitch a minute after replacing Stephen Welsh when his attempt to head away a bouncing ball went all wrong as he presented Waide with the chance to rifle the ball home from six yards.
Dylan Boyle's trip on Mackay as the wide man drove into the box handed Middleton his chance from the spot, with the Ibrox man slotting the resulting penalty home confidently for the narrow win.