"Coronation Street" bosses have found it "quite tough" to schedule Charles Lawson's comeback.
Series producer Kate Oates has admitted it has been hard trying to pin the 58-year-old "Corrie" legend down to film scenes as soap hard-man Jim McDonald, because he has been so busy working in theatre.
She exclusively told BANG Showbiz: "I think he will always have that part of Jim McDonald running through him but he's got other stuff happening.
"He's working in theatre, so scheduling him is quite tough, but we've not started filming yet.
"I'm excited to see him back."
But Charles - who is to star in a theatre production of "Rebus" - has revealed he will be filming his "Corrie" comeback in July and August.
The star told fans the news while responding to one of his Twitter followers, who asked the actor if he wanted to attend the Killarney horse racing track in the Irish town in July or August, but he will be too busy shooting "Corrie" at the time.
He replied: "I would love that me old pal, but that's when I'm filming something called " Coronation Street "? (sic)"
The fan then joked he should call in sick, but Charles quipped he couldn't possibly do so because he is "irreplaceable" in the soap.
He tweeted: "Irreplaceable mate!! (sic)"
Charles" character Jim looks set to return to the cobbles with a muscle-wasting condition.
The ITV soap are to explore the issue when the no-nonsense convict makes his comeback, nearly two years after he told son Steve McDonald (Simon Gregson) he could have genetic disorder myotonic dystrophy.
Kate recently said: "We played a story 18 months [ago] where it seemed like Steve might have inherited a genetic disease from his dad, but no one went to see Jim to ask if he was OK.
"We have a great story to play with that."
Charles previously admitted show bosses were keen to sign him up full-time this year, but he couldn't commit due to other filming duties.
He said: "They wanted me back full time this year but I couldn't do it as I am doing "Rebus" on stage, and a thriller.
"I'm going to film a bit but then will be back again next year."