Millwall's Under 23s suffered defeat against Charlton Athletic in the Professional Development League at the Calmont Road training ground.
The young Lions, who fell to The Addicks in the reverse fixture just eight days ago, sought to make amends on home soil on Tuesday afternoon, but found themselves chasing the match after just five minutes.
A cross was steered in from the left and met by Terrique Anderson, who drilled beyond the reach of Millwall goalkeeper Ryan Sandford.
However, the hosts didn't have to wait long for an opportunity to equalise and when a corner was lofted towards the awaiting Lions pack in the 18th minute, Christian Mbulu was well placed to fire into the bottom corner after a mad scramble in the box.
The Lions had the first sight of goal after the restart with Isaac Olaofe seeing a shot saved by Harvey, but as the clock ticked over to the hour mark, The Addicks saw their lead restored courtesy of an own-goal.
Charlton's Jamie Mascoll swung in a corner and a Millwall defender sliced the ball back into the net while looking to clear his lines.
The remainder of the match was a scrappy affair as the visitors dug in to secure the three points.