A Russian court has rejected a lawsuit filed by the mother of Alexei Navalny, the Russian opposition stalwart who died in prison in February, that claimed he received inadequate medical care, a close Navalny colleague said Thursday.

Ivan Zhdanov, head of the Anti-Corruption Foundation that was started by Navalny, said the court in the town of Labytnangi, near the Arctic prison where he died, turned down the suit because it said only Navalny himself could be the plaintiff.

“Alexei filed claims against the colonies many times for failure to provide medical care. The claims were denied. Now that he was killed, his family’s claim is being denied with mocking wording,” Zhdanov said on the Telegram messaging app.

Navalny, the most persistent foe of President Vladimir Putin, was serving a 19-year sentence. He had been behind bars since January 2021 after returning to Russia from Germany where he had been recovering from nerve-agent poisoning that he blamed on the Kremlin.

The cause of his Feb. 16 death has been described by officials only as due to natural causes.