If, in nodeGame, I do node.game.memory.add({player: node.player.id, stage: node.player.stage, data: { "foo": null }}); node.game.memory.save("data.json"); I get { "player": "681934395222262", "stage": { "stage": 2, "step": 1, "round": 1 }, "data": { "foo": "!?_null" }, "timestamp": 1516569132070 } where instead I would have expected something like { "player": "681934395222262", "stage": { "stage": 2, "step": 1, "round": 1 }, "data": { "foo": null }, "timestamp": 1516569132070 }