Christoph Waltz has dropped out of David Cronenberg’s The Talking Cure and will be replaced with Viggo Mortenesen.

According to Deadline Hollywood, Waltz was to play Sigmund Freud in the film, set to start shooting in May. Based on the play by Christopher Hampton, The Talking Cure is about the relationship between Freud and his pupil Carl Jung. But the Austrian actor — who won this year’s Best Supporting Actor Oscar for his portrayal of a Nazi in Inglourious Basterds — has signed on to play a psychotic animal trainer in Water For Elephants, and this meant walking away from the Cronenberg picture.

Deadline says his departure left producers scrabbling for a replacement and there were fears they would have to scrap production completely. Fortunately Viggo Mortensen, who previously worked with Cronenberg on A History of Violence and Eastern Promises, has stepped into the role and will star as Freud opposite Michael Fassbender as Jung. Keira Knightley will play Sabina, a disturbed young Russian woman brought to see Jung by her father. A romantic relationship develops between Jung and Sabina.

Deadline says the film will feature lots of “spirited sex.”