The new Star Wars movie is already being filmed, and most of the cast for the latest installment — Episode VII — has already been chosen, said Disney Studios chairman Alan Horn.

Horn, whose studio is producing the film, said of the cast for the upcoming Star Wars movie, due in 2015, “We have a lot of them … We’re just not completely done yet,” the Hollywood Reporter reports. Horn added that casting has been the greatest difficulty in getting the latest Star Wars launched.

Speculation has surrounded casting for the movie for some time, with rumors flying that Adam Driver of HBO’s Girls will play the villain in the new Star Wars installment and reports of talks with Lupita Nyong’o, who starred in 12 Years a Slave, as a female lead.

But in response to further questions about the cast, Horn adopted a Yoda voice. “Patience, you must have,” he said.

The screenplay for the film has been completed, and was written by J.J. Abrams and Lawrence Kasdan following an early draft by Michael Arndt.

Horn said the film will be released in December 2015.

[THR]

Contact us at letters@time.com.