A late double from substitute Shane Ferguson saw Millwall come from behind to beat Hull City 2-1 at the Den.
The visitors looked on course to progress to the next round when Jon Toral combined well with Nouha Dicko to open the scoring early in the second period (52).
The goal was arguably against the run of play with Millwall having the better of the first-half chances – Aiden O’Brien firing wide from Tom Elliott’s flick-on as well as seeing a header cleared off the line.
And with the Lions becoming increasingly frustrated, boss Neil Harris made a triple substitution just after the hour mark which turned the game in their favour.
It was one of these changes, Ferguson, who not only found a 82nd minute equaliser but then sealed Millwall’s passage into the Fourth Round three minutes later.
The winger first found an equaliser after a well-worked short-corner routine before rifling home a free-kick to ensure Millwall reached the next round for the third consecutive season.