Andy Lonergan might have been looking for somewhere to hide after his New Year howler at Hillsborough.
But instead the keeper stepped up to the plate and produced a string of saves to send Preston in the fourth round.
Simon Whaley's 47th-minute strike was the difference between the two sides as North End gained revenge for a double reverse in the league.
But it was only thanks to Lonergan that Preston weren't dead and buried before Whaley hit the jackpot. Apart from a bad early miss by Neil Mellor, Scunthorpe - inspired by Jack Cork - dominated the first half.
And Preston were grateful when Lonergan denied Martin Paterson in the 13th minute before blocking Matt Sparrow's effort 12 minutes later.
Simon Morris should have netted the rebound and Lonergan saved from Kevan Hurst before Paul Hayes fluffed another chance on 38 minutes.
And after another Mellor miss, Lonergan rounded off a grim day for United with a late save from Hayes.
"I'm gutted," groaned Iron boss Nigel Adkins. "We created chances but just couldn't put the ball in the net."
Preston chief Alan Irvine said: "I spoke to Andy after the Wednesday game. He needed to move on and I'm delighted he kept a clean sheet."
Preston: *LONERGAN 8 - Davidson 6, Mawene 6, Chilvers 5, Hill 6 - Whaley 6, McKenna 7, Carter 5, L Neal 6 - Hawley 6, Mellor 5 (Ormerod, 87mins).
Scunthorpe: Murphy 6 (Lillis, 72mins, 5) - Byrne 6, Crosby 7, Martis 6, Williams 6 (Forte, 68mins, 6) - Hayes 5 (Ameobi, 87mins), Sparrow 6, Morris 6, *CORK 8, Hurst 7 - Paterson 6.
Ref: C Webster 6.