Lafferty now has ten goals for his Serie B club.
"Winning a match of that kind was very important," Lafferty said to Palermo24.net. "But let's not forget we are playing again on Thursday.
"It was a special occasion but the important thing was the three points.
"A lot of people say the Glasgow derby is the best in the world and I agree, the Old Firm game is incredible.
"I never set myself limits but if I can score 15 goals I would be very happy. The important thing is that the team is successful."