This summer, the Ukrainian government awarded the rights to develop a huge complex of oil and gas fields in the country to an American company that is co-owned by a former campaign donor to then-Energy Secretary Rick Perry. The decision annoyed the heads of the state-owned Naftogaz conglomerate, which had competed and lost the bidding for the contract. Now, Naftogaz has filed a lawsuit seeking to overturn the deal, two sources familiar with the matter tell TIME, casting a spotlight on Perry’s role in Ukraine’s oil and gas industry.

The suit was filed on Friday afternoon in the District Administrative Court of Kyiv, the sources tell TIME, and has not been previously reported. In a draft of the complaint obtained by TIME on Monday, Naftogaz alleges that the government of Ukraine acted illegally and with bias in July when it granted the oil and gas fields to an American company that is co-owned by Michael Bleyzer, one of Perry’s longtime allies and financial backers.