On 5 May 2021, he extended his contract with Zenit throughout the 2023–24 season.[5] On 10 October 2023, Mostovoy extended his contract with Zenit once more until June 2027 with an option for the 2027–28 season.[6]
International career
Mostovoy was called up for the Russia national team for the first time for UEFA Nations League games against Serbia and Hungary in September 2020.[7] He made his debut on 8 October 2020 in a friendly against Sweden.[8]
On 11 May 2021, he was included in the preliminary extended 30-man squad for UEFA Euro 2020.[9] On 2 June 2021, he was included in the final squad.[10] On 11 June 2021, he was removed from the squad after testing positive for COVID-19 and replaced by Roman Yevgenyev.[11]