David Dickinson has taken over as referee for St Mirren and Rangers' Betfred Cup showdown.
Andrew Dallas was poised to be the man in the middle but has been forced into a late withdrawal through injury.
Dickinson, who was originally appointed as fourth official, will now take over from the injured whistler.
It's a huge turn of events for the rookie whistler, who has taken charge of mainly League One and Two clashes this season.
Rangers visit Paisley to face the Buddies for a place in the last four draw, set to take place later on Wednesday night.
Ibrox boss Steven Gerrard admits he's expecting a tough test against Jim Goodwin 's side, who are unbeaten in nine matches.
Gerrard said: "They’re a good side.
"They’ll be well organised, they’ll make it really difficult for us, and they’re a team in good form.
"But for me the focus is always on us. The players deserve to stay in the team.
"We’re ready, the players have prepared well, and we’re looking forward to the challenge in front of us."
Hibs and St Johnstone have already secured their places at Hampden for the semis.
