In the 20 months of Russia’s wider war on Ukraine, the Ukrainian army has captured around 200 of Russia’s T-72B3 tanks.

The T-72B3, a product of Uralvagonzavod in Nizhny Tagil, is one of Russia’s newer tanks. And unlike, say, the T-64BV, the T-80U or the T-72AMT, Ukrainian industry doesn’t have much experience with the type.

So when a Ukrainian tanker with the callsign “Kochevnik” ran into problems with his captured Russian T-72B3—problems local expertise couldn’t immediately solve—he called Uralvagonzavod tech support. And incredibly, the help line actually helped.

Militarnyi captured Kochevnik’s calls on video.

Kochevnik serves in the Ukrainian army’s 54th Mechanized Brigade, which fights around Kramatorsk in eastern Ukraine and operates mostly Soviet-vintage equipment including T-64 tanks and BMP fighting vehicles. It also owns some of Ukraine’s ex-Russian T-72B3s.

Kochevnik was trolling the Russians, mostly. But his gripes with his 45-ton, three-person tank were real. The tank had been spewing oil. Its compressors weren’t working. The electrical turret-rotation mechanism kept failing, forcing the crew to rotate the turret with a hand crank.

While any tank can be temperamental, the list of malfunctions Kochevnik was dealing with might speak to inconsistent workmanship at Uralvagonzavod’s factories.

A Russian who gave his name as Aleksander Anatolevich, who clearly was unaware that Kochevnik is a Ukrainian soldier, promised he’d bring up the problems with the design bureau in Nizhny Tagil—and that he’d also contact the engine-manufacturer in Chelyabinsk.

Kochevnik wasn’t done trolling. He also got ahold of Andrey Abakumov, a Uralvagonzavod director. Abakumov asked Kochevnik to describe the tank’s problems in detail on WhatsApp.

That’s when Kochevnik finally revealed he’s Ukrainian, and his army had captured the problematic T-72 around Izium late last year.

Laughing, Kochevnik ended the call.