LOS ANGELES (AP) — 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 Screen Actors Guild-American Federation of Television and Radio Artists said Llama Productions, a subsidiary of gaming giant Epic Games, “failed and refused to bargain in good faith with the union” in the last six months. The company made unilateral changes to the terms and conditions of employment “without providing notice to the union or the opportunity to bargain” by using AI-generated voices to replace bargaining unit work, SAG-AFTRA said.

Epic Games did not immediately respond to a request for comment.

SAG-AFTRA called a strike against major game companies in July after more than a year of negotiations around the union’s interactive media agreement broke down over concerns around the use of unregulated artificial intelligence.

In a statement, SAG-AFTRA said the union supports the rights of members and their estates to control the use of their digital replicas.

“However, we must protect our right to bargain terms and conditions around uses of voice that replace the work of our members, including those who previously did the work of matching Darth Vader’s iconic rhythm and tone in video games,” the union said.