Fox has filed a confidential lawsuit against Flutter, the U.K.-based majority owner of FanDuel, to secure its option to buy into FanDuel Group at the same price Flutter paid in December — a much lower price than what Flutter believes FanDuel is worth today.

Fox wants to acquire an 18.6% stake in FanDuel at an $11.2 billion valuation — the value set when Flutter acquired a 37.2% stake in FanDuel from Fastball in December. But Flutter has argued Fox must pay “fair market value” to exercise the option in July. That price could be determined by a FanDuel initial public offering, which Flutter is considering. If FanDuel isn’t spun out by July, Flutter has said that banks will determine FanDuel’s fair value.