<math> problem

[Dennis Putnam]

I have the following sequence:
<echo message="${serialnumber} - ${membernumber} - ${name} - ${keystring}" /> <math result="serialnumber" operand1="${serialnumber}" operation="+" operand2="1" datatype="int" /> <echo message="${serialnumber} - ${membernumber} - ${name} - ${keystring}" />
The first echo generates the following as expected:

[echo] 1001 - 60286 - -

At that point the build fails on the math task. The error says, Cause: The name is undefined.

Since it is obvious that it cannot be referring to ${serialnumber}, I have no clue to what "The name" refers. Can anyone shed any light on this? TIA.

[Dennis Putnam]

Never mind, I figured it out. I needed to add <taskdef> pointing to the ant-contrib jar which has to be installed separately.