When specifying the details for the payment object I have noticed that if I leave amount blank I am not prompted to enter an amount by the bitcoin-qt 0.9 client.

xpd = x.PaymentDetails()
xpd.time = int(time())
xpd.outputs.add(amount = 10000000, script = serialized_script)
xpd.memo = 'this is xpd memo'
xpdstring = xpd.SerializeToString()
xpr = x.PaymentRequest()
xpr.serialized_payment_details = xpd.SerializeToString()
xprstring = xpd.SerializeToString()

If I do not specify an amount then it is set to zero by default and I am presented with the error that the bitcoin amount is too small and is considered 'dust'.

Please can someone help me understand how to prompt the user for a deposit amount if the amount field is blank?

Thanks.

Additionally I should note that I am using the testnet.