Lee Gregory's second-half penalty secured a vital three points for Millwall in Tuesday night's 1-0 win over Peterborough United at The Den.
The striker's 12th of the campaign ensures a 16th match unbeaten for The Lions, with the shut-out taking the club's clean sheet run to 9.
Neil Harris made three changes to the starting line-up that drew 0-0 with Oldham Athletic on Saturday, as Shane Ferguson, Fred Onyedinma and Ben Thompson replaced Aiden O'Brien, David Worrall and Calum Butcher, who all dropped to the substitutes bench.
The Lions started the brighter and passed the ball around well, but failed to work Posh goalkeeper Luke McGee until Shaun Williams' dipping effort hit the post behind the goal on 9 minutes.
Tom Nichols registered Peterborough's first shot on goal on 22 minutes, but his tame effort was not enough to trouble Tom King.
King, however, was troubled just three minutes later, but he reacted well to palm Marcus Maddison's free-kick to safety.
Williams got the Den crowd going with a few thunderous challenges shortly before the half-hour mark, but after he laid the ball off to Ferguson, the Northern Irishman's dangerous cross was headed away.
On 42 minutes, Maddison's cross fortunately evaded everyone as Peterborough looked to open the scoring. That proved to be the last action of note in an otherwise eventful half.
On 53 minutes, The Lions took the lead from the penalty spot. Gregory picked the ball up on the halfway line and went on a lung-busting run before he was halted inside the box. The striker dusted himself down and slotted his kick low to the right of McGee to nudge Millwall in front.
The Posh nearly equalised four minutes later, however after a bout of ping-pong inside the Millwall penalty area, Andrew Hughes' header looped on to the top of the net.
King saved well from another Maddison free-kick as the hour-mark struck, whilst the other end, substitute O'Brien tested McGee.
Thompson stung the palms of McGee with eight minutes remaining, with Cooper also heading into the arms of the goalkeeper on 85 minutes.
Gregory received a standing ovation as he was replaced by Butcher with two minutes remaining and after five minutes of stoppage time, the striker was safe in the knowledge that his goal had secured a 16th match unbeaten for The Lions.
Millwall: King, Cummings, Craig, Williams, Thompson (Hutchinson, 90+3'), Gregory (Butcher, 88'), Onyedinma, Webster, Ferguson, Cooper, Smith (O'Brien, 65'). Subs not used: Girling, Worrall, Romeo, Abdou.
Scorer: Gregory (54')
Peterborough United: McGee, Smith (Angol, 88'), Hughes, Bostwick, Tafazolli, Taylor, Maddison, Inman, Da Silva Lopes (Mackail-Smith, 65'), Nichols, Grant (Forrester, 74'). Subs not used: Tyler, Binnom-Williams, Samuelsen, Morias.
Bookings: Maddison, Inman
Referee: Kevin Johnson
Attendance: 8,032 (303)