Gematsu spotted the classification listing online, although it has seemingly since been pulled by the ratings body.
Doom 64 launched exclusively on Nintendo 64 in 1997. The game features brand new graphics, gameplay elements and a modified version of the Doom engine.
Bethesda was unavailable for comment at the time of publication.
The classification was spotted late last week, around the same time Bethesda announced surprise releases for the original Doom, Doom 2 and Doom 3 on consoles and mobile devices.
The launches coincided with the QuakeCon 2019 convention, which had a heavy Doom focus to commemorate the 25th anniversary of the influential shooter series.
The latest Doom instalment, Doom Eternal, will release on November 22, 2019.
During the Doom Eternal keynote presentation at QuakeCon, which you can view in the video above, id Software executive producer Marty Stratton and creative director Hugo Martin showed off some of the game’s campaign and offered a fresh look at its multiplayer experience, Battlemode, which sees one fully-armed Doom slayer taking on two player-controlled demons in round-based battles.
For more on the game, see VGC’s recent Doom Eternal interview with Stratton and Martin.