Error: Unsupported Key Schema in Record Definition

const TimePeriod = S.Union(
  S.transformLiteral("daily", "24h"),
  S.transformLiteral("weekly", "7d"),
  S.transformLiteral("monthly", "30d"),
  S.Literal("lifetime"),
);
 const MySchema = S.Record({
  key: TimePeriod,
  value: S.Record({ key: S.String, value: S.Int.pipe(S.nonNegative()) }),
});

error: Uncaught (in promise) Error: Unsupported key schema
schema (Transformation): ("daily" <-> "24h")