Having snatched a victory against the run of play against Crystal Palace on Boxing Day, Millwall fell to exactly the same trick at The Den two days later, as Gillingham came away with three points.
Millwall started more brightly, before falling behind midway through the first half to a deflected strike from Gills player-manager Andy Hessenthaler, as the ball bounced off Mamady Sidibe to leave Tony Warner stranded in the Millwall goal.
The Lions still created the majority of chances through loan signing Nick Chadwick and Neil Harris, but were forced to wait for the 55th minute before levelling, when Chadwick turned home Tim Cahill's cross to give them renewed hope.
Millwall player-manager Dennis Wise had replaced the lively Aboubaka Fofana at the break, in the hope of forcing his side to become more direct and it certainly appeared to be working as the Lions enjoyed by far the better of the second half.
Chadwick had further chances to claim a winner, while Wise himself will look back on a cross shot which slid past the far post and wonder how his side ended the game empty-handed.
Gillingham had former Charlton youth prospect Kevin James to thank for their victory. Picking up the ball in the centre of midfield, James weaved his way goalwards before unleashing a stunning strike to leave Warner grasping at thin air and Gillingham celebrating a victory as dramatic as it was unlikely.
Having gone into the game with vague hopes of a play-off place still to play for, it was a cruel blow for the Lions, and the next few weeks will tell us much about their resolve.
For Gillingham, having been relegation candidates a few weeks ago, their horizons are suddenly considerably brighter.