Hollywood’s actors’ union filed an unfair labor practice charge against Llama Productions on Monday, alleging the company replaced actors’ work by using artificial intelligence to generate Darth Vader’s voice in Fortnite without notice.

The actors’ union that began striking against video game companies last summer has filed an unfair labor practice charge against Epic Games, the creator of Fortnite.

Sag-Aftra says the hit video game has used tech to replace human performers.