Vladimir Putin has submitted a draft amendment to Russia’s constitution that would enshrine marriage as between a man and a woman in a conservative update to the country’s founding document.

The measure was reportedly part of a 24-page document submitted by the president that would also name Russia as the successor to the Soviet Union; explicitly mention Russians’ “faith in God”; and ensure the “defence of historical truth” regarding the Soviet role in the second world war.

The amendments would also proscribe the cession of Russian territory to foreign powers, deepening the conflict over the Kremlin’s annexation of Crimea.

The draft submissions have not yet been made public but were described to journalists in a series of briefings by high-ranking members of the Duma, the lower house of the Russian parliament.

“For me, the most important proposal would fix the status of marriage as a union between a man and a woman,” Pyotr Tolstoy, a vice-speaker in the Duma, told reporters on Monday in remarks carried by Russian state news agencies. “And I am happy that this amendment has appeared under the signature of the head of state.”

Russia is planning to amend its constitution for the first time since 1993. The move, announced by Putin in January, was initially seen as a way for him to hold on to power after 2024, when as things stand he will no longer be able to serve as president because of term limits. After a parliamentary vote, Russia will hold a nationwide referendum in mid-April, when the conservative amendments may help boost turnout.

Putin’s direct support for the amendments makes it likely they will go through. He has taken an increasingly conservative turn in his fourth term as president, and has enjoyed support from both patriotic groups and the Russian Orthodox church.