DraftKings (DKNG) has asked a US Patent and Trademark Office tribunal to invalidate a patent asserted against the gaming operator by Interactive Games, according to a petition filed Thursday.

DraftKings argued that all 18 claims of the patent are unpatentable as obvious in light of prior art, the filing said. The patent involves a mobile wagering system that uses location information, among other features, to prevent users from placing wagers outside permitted gaming areas.

Interactive Games asserted the patent against DraftKings in an April lawsuit, according to the petition.

Bloomberg earlier reported that the patent is one of five Interactive Games patents asserted against DraftKings and that the gaming operator has sought dismissal of the case, arguing that the patents are abstract and ineligible for protection under Section 101.

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