firmata analog read limit

Hi guys,

Do all firmata protocols available support only upto A5 pins?

I'm using pyfirmata on python to graph live reading from the arduino DUE.

Sensors from A0 to A5 work perfectly until I add A6 and above.

a6 = due.get_pin('a:6:i')

raise InvalidPinDefError('Invalid pin definition: {0} at position 3 on {1}'
pyfirmata.pyfirmata.InvalidPinDefError: Invalid pin definition: a:6:i at position 3 on COM10

I believe this is somewhat a known issue. Looking for a quick fix.

Thanks,