Can `Schema.Class` Struct be Mutable?

export class Person extends S.Class<Person>('Person')(
  S.mutable(
    S.Struct({
      name: S.String,
      age: S.Number,
      address: Address // an immutable value object Schema
    })
  )
) {}

Argument of type 'mutable<Struct<{ name: typeof String$; age: typeof Number$; }>>' is not assignable to parameter of type 'Fields | HasFields<Fields>'.
  Type 'mutable<Struct<{ name: typeof String$; age: typeof Number$; }>>' is missing the following properties from type 'Struct<Fields>': fields, records, make