NEW YORK (AP) — Production on a new season of “The Big Bang Theory” is being delayed because of a contract dispute with its top actors.

The Warner Brothers Television studio, which makes television’s most popular comedy, said that Wednesday’s scheduled first day of work after the summer hiatus was postponed. There’s no word on when “The Big Bang Theory” team will be back at work.

The CBS series is heading into its eighth season, and the studio is trying to hammer out new deals with actors Jim Parsons, Johnny Galecki, Kaley Cuoco, Simon Helberg and Kunal Nayyar.

Contract disputes aren’t unusual at popular, long-running TV series, and CBS Entertainment Chairman Nina Tassler seemed to take it in stride when asked about the negotiations two weeks ago.

“I just love being able to answer these questions year after year, primarily because we have successful shows,” she said. “And when you have successful shows, you have renegotiations. We’re feeling very confident that everything will work out. These deals manage to get done somehow miraculously year after year.”

CBS had no additional comment on the negotiations Wednesday.

It’s considered far too early for such a dispute to affect the timing of a show’s season premiere. “The Big Bang Theory” opens its new season on September 22. The show is moving temporarily to Mondays for the beginning of the new season with CBS airing NFL football games on Thursdays for the first half of the season.