Support for numbers as short options

We have the following options definition:

[Option('1', "readlog1", HelpText = "Reads log entries from the Log 1 memory.")]
public bool ReadLog1 { get; set; }

[Option('2', "readlog2", HelpText = "Reads log entries from the Log 2 memory.")]
public bool ReadLog2 { get; set; }

It looks like the short options don't work because they are numbers.
Is there any special reason for this?