Barnet missed the chance to cut the gap at the top of the Vanarama National League as they were comprehensively beaten 4-1 at home by Oldham.
A win at the Hive would have seen the hosts draw to within five points of leaders Chesterfield but they fell behind after 26 minutes when goalkeeper Laurie Walker brought down Mike Fondop and conceded a penalty, which James Norwood converted.
Walker had initially been shown a red card before the referee rescinded the decision and issued a yellow.
Barnet looked to have taken advantage of the reprieve when Harry Pritchard levelled from the spot 10 minutes into the second half.
But from there the visitors took control, Fondop restoring the lead before Norwood got his second from 12 yards.
Hallam Hope netted in the 90th minute to make it back-to-back wins and move Oldham to within two points of the play-off places, while Barnet fell to a third straight loss.