China will buy 24 Sukhoi Su-35 fighter jets from Russia in a deal worth more than $2 billion, an industry source told Reuters on Thursday, in a move that may help the Kremlin’s strained finances.

A spokeswoman for Russian state conglomerate Rostec confirmed a deal between the two countries had been signed involving Su-35 fighter jets, but declined to provide details.

The deal makes China the first foreign buyer of the Su-35, one of Russia’s most advanced military aircraft, and is one of the largest contracts for military jets ever signed between the two countries.

Chinese state media quoted Russian media on the deal. The Chinese government has not commented, in keeping with standard practice on arms deals.

Russia and China have been in talks for several years over the Su-35s, and in 2012 the two sides signed a preliminary agreement for Beijing to buy some of the jets, the Kommersant newspaper reported.

Arms sales are a rare bright spot in an otherwise gloomy economic picture for Russia, whose economy is suffering from weak oil prices and Western sanctions over the Ukraine conflict.