field.length undefined in typeCast function

[sgerace]

I'm trying to implement a typeCast function on my conenction pool to convert TINYINT(1) to boolean, as provided in the documentation:

var sqlpool = mysql.createPool({
  host: [...],
  user: [...],
  password: [...],
  timezone: 'Z',
  typeCast: function (field, next) {
    if (field.type == 'TINY' && field.length == 1) {
      return (field.string() == '1'); // 1 = true, 0 = false
    }
    return next();
  }
})

However, I'm always getting undefined for field.length (regardless of field type) so this is currently failing. Is there something else I need to enable to get the field length, or is something else going on here?

Thanks!