Russian gas giant Gazprom took a 213 billion rouble ($3.4 billion) impairment in relation to its legal row with Ukraine, it said.

Gazprom’s full-year net income fell by a quarter to $11.4 billion, it had said, citing higher debt and the legal costs related to the dispute with Ukraine over gas supplies and transit to Europe, according to Reuters.

The legal costs were reflected in “other operational costs” in Gazprom’s 2017 report, deputy chief accountant, Mikhail Rosseyev, said in a conference call with investors on Friday.

The legal dispute in the Stockholm arbitration court is a byproduct of a broader political row between ex-Soviet states, Russia and Ukraine.

Gazprom has to pay Ukraine $2.56 billion after a Stockholm court found in Naftogaz’s favour in the final stage of a long-running legal battle in February.

That ruling is being challenged by Gazprom in the same court and it also lodged a filing seeking to terminate contracts with Ukraine on gas supplies and transit.

Ukraine is the main route for Russian gas exports to the European Union.