Daniel Majstorovic and Scott Brown grabbed the goals which gave Celtic a 2-0 win at Berwick Rangers and a place in the Scottish Cup fifth round.
The win also meant the Glasgow giants avoided a repeat of last year's embarrassment, when they were defeated in the semi-finals by Ross County.
"It was solid but it wasn't spectacular and we expected that to be the case today with the pitch and the conditions," said Celtic manager Neil Lennon.
"We had to play in a different way because the pitch didn't suit the way we like to play. It's another clean sheet and we are pretty pleased.
"These games are always difficult and they are always scrappy affairs. We were quite comfortable in the game and once the second goal went in I felt we could have won the game more comfortably."
Celtic's new signing Freddie Ljungberg made his debut at Berwick's tiny Shielfield Park after recovering from the virus that kept him out of last week's Old Firm derby win.
Lennon said: "It was difficult for him to have an impact on the game because it was quite congested in there.
"But the 60 minutes will have done him the world of good and the longer he trains and plays, there will be more opportunities for him to show what he can do."