PUBG Corp is taking Epic Games to court in South Korea over accusations that Epic Games copied intellectual property to create Fortnite Battle Royale.

“This is a measure to protect our copyrights,” a PUBG representative told Bloomberg News.

This isn’t the first time PUBG Corp has accused Epic Games of copying its designs on Playerunknown’s Battlegrounds (PUBG) for the increasingly more popular Fortnite Battle Royale. The corporation filed an in injunction in January against Epic Games Korea, according to the BBC. Epic Games is now accused of copying PUBG Corp’s weapon designs as well as the user interface from PUBG.

While both games employ similar gameplay traits— Fortnite Battle Royal and PUBG both drop 100 players into a map and make them battle it out until only one person, or one team, is left standing — there are some notable differences between PUBG and Fortnite Battle Royale. Fortnite encourages players to build forts and craft items in order to defend themselves and better their attacks, while PUBG hasn’t incorporated any building skills in the game at this point.

Fortnite has continued to grow in popularity while attention to PUBG has struggled to match that game’s immense popularity. Epic’s Battle Royale mode launched in September 2017, just a few months after Fortnite’s initial launch in July of that year. Fortnite remains the most watched game on Twitch, according to analytics site TwitchMetrics, averaging an impressive 187,000 viewers in May. PUBG, however, only averaged an approximate 52,000 viewers this month; a 9 percent decrease in viewership. Even streamers like Dr DisRespect have called out the player base jumping from PUBG to Fortnite.

“The game is slowly dying,” Dr DisRespect says in the video above. “Until they change the player mechanics and optimization, it’s never going to succeed at the Fortnite level. Ever!”

Update: An Epic Games representative told Polygon the company doesn’t comment on ongoing litigation.