Paypal Payment Pro not passing along CVN

When testing out Paypal's WPP in e-commerce, I was getting the error:

This transaction cannot be processed without a Credit Card Verification number.

It seems that the cvn was not getting passed. To fix the bug, I added 'CVV2' to the $params array in paypal.module line 488 in function paypal_pro_receipt_process_payment. So now it looks like:

  $params = array(
    'PAYMENTACTION' => 'Sale',
    'CREDITCARDTYPE' => strtoupper($payment_form['cardtype']),
    'ACCT' => $payment_form['cardnumber'],
    'CVV2' => $payment_form['cvn'],
    'FIRSTNAME' => $fname,
    'LASTNAME' => $lname,
    'EXPDATE' => $payment_form['expiry']['expmonth'] .'20'. $payment_form['expiry']['expyear'],
    'AMT' => number_format($total),
    'IPADDRESS' => $_SERVER['REMOTE_ADDR'],
  );