Cristiano Ronaldo must always score Juventus' penalties so he can be forgiven for haunting the club in last season's Champions League, coach Massimiliano Allegri said.

Ronaldo's 98th-minute penalty for Real Madrid saw the LaLiga giants knock Juve out of Europe in a controversial quarter-final tie in April.

The Portuguese superstar has since joined the Italian outfit, and he took his tally to 11 goals in 18 games with a spot-kick in a 3-0 win over Fiorentina on Saturday.

Asked about Ronaldo taking his side's penalties, Allegri said it was one way for the 33-year-old to be forgiven for his heroics against Juve in Europe.

"Ronaldo takes the penalties," he told a news conference.

"After he's scored that one against us in the 93rd minute at 139km/h, am I supposed to let somebody else do that?

"He has to do something to be forgiven. He's got to take penalties and score... always."

Ronaldo became the first Juve player since John Charles (1957-58) to score at least 10 goals in his first Serie A season after matchday 14.

Juve are 11 points clear atop Serie A after their 13th win.