Elon Musk’s X has added live-streaming service Twitch to its lawsuit claiming dozens of companies conspired with an advertising industry group to boycott the social media platform, causing it to lose revenue.

Musk named Twitch as a defendant in an amended lawsuit filed on Monday night in federal court in Wichita Falls, Texas. California-based Twitch is a subsidiary of Amazon.com, which was not named in the complaint.

The original August lawsuit accused the World Federation of Advertisers, CVS Health, candy maker Mars, and Danish renewable energy company Orsted of conspiring along with others to withhold “billions of dollars in advertising revenue” from X, previously known as Twitter, after Musk bought the company.

X said the defendants formed a "group boycott" that violated U.S. antitrust law by hampering the free flow of ad dollars.

Twitch and its parent Amazon did not immediately respond to a request for comment, and neither did X.

The other defendants have not yet responded in court to X’s claims and either declined to comment or did not immediately respond to comment requests on Tuesday.

Monday's amended lawsuit formally dropped Unilever as a defendant, after the company said in October that it had reached an agreement with X.

World Federation of Advertisers launched an initiative in 2019 to “help the industry address the challenge of illegal or harmful content on digital media platforms and its monetization via advertising.”

Following Musk's purchase of Twitter in October 2022, some advertisers were wary that ads for their brands would appear next to harmful content, such as racist or false posts, that might have been removed under prior management. Ad revenue at X slumped for months after the Twitter sale.

Twitch purchased no advertising from Twitter in the United States after November 2022, according to X’s lawsuit.

Musk has gained new prominence as a key force in U.S. President-elect Donald Trump's incoming administration, including in a newly-created role designed to cut government waste. Musk donated millions of dollars to Trump's Republican campaign.