xmlrpc server returns error even when optional arguments are passed

While testing a new module built on Services 6.x-3.0-rc3, I found errors while calling node.retrieve using xmlrpc. After further testing I found the following code at line 69 of servers/xmlrpc_server/xmlrpc_server.module:

if(is_array($controller['args'])) {
foreach($controller['args'] as $index => $arg) {
if($arg['optional'] && isset($arg['default value']) && !isset($args[$index])) {
$args[$index] = $arg['default value'];
} else {
if($arg['optional'] == FALSE) {
return services_error(t('Missing required argument @arg', array(
'@arg' => $arg['name'],
)), 401);
}
}
}

This appears to result in an error for every required argument even if it is passed in. The issue was corrected by changing the last if condition to the following:

if($arg['optional'] == FALSE && !isset($args[$index])) {