Action with "Guid?" is not working

[juniorgasparotto]

public string Get(
EntityNames type,
[Argument(ShortName = 'i', LongName = "id")] Guid? id = null,
[Argument(ShortName = 'b', LongName = "bank-id")] string bankId = null,
[Argument(ShortName = 'n', LongName = "name")] string name = null,
[Argument(ShortName = 'a', LongName = "agency")] string agency = null,
[Argument(ShortName = 'c', LongName = "account-id")] string accountId = null,
[Argument(ShortName = 'o', LongName = "output")] string outputFormat = null
)
{
}