MK Dons conceded a stoppage time penalty as they went down 2-1 to Millwall on Saturday.
Robbie Neilson said referee Ross Joyce had been tricked by the crafty Lee Gregory, who appeared to be fouled by Paul Downing in the dying minutes at The Den with the scores tied at 1-1.
Gregory opened the scoring after 25 minutes as he headed home Shane Fersugon's cross, but the lead would last just five minutes as Ben Reeves pulled Dons level - the first goal Millwall had conceded in nine games.
The result sees Dons remain 14th in League 1.
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