public function addInputPrefix(MethodInvocation $invocation)
    {
        $helper = $invocation->getThis();
        $args = $invocation->getArguments();
        if (!empty($args[0]) &&
            is_string($args[0]) &&
            $helper instanceof FormHelper
        ) {
            $args[0] = $this->_fieldName($helper, $args[0]);
        }
        $this->setProperty($invocation, 'arguments', $args);

        return $invocation->proceed();
    }