System.xml "select" with a custom Model not working

Question

app\code\local\Jurgis\Twilio\etc\system.xml

<language translate="label">
          <label>Voice Language</label>
          <frontend_type>select</frontend_type>
          <source_model>Twilio/Language</source_model>
          <sort_order>92</sort_order>
          <show_in_default>1</show_in_default>
          <show_in_website>1</show_in_website>
          <show_in_store>1</show_in_store>
</language>

app\code\local\Jurgis\Twilio\etc\config.xml

<?xml version="1.0"?>

<config>
    <modules>
        <Jurgis_Twilio>
            <version>1.0.0</version>
        </Jurgis_Twilio>
    </modules>
    <global>
      <helpers>
          <Jurgis_Twilio>
            <class>Jurgis_Twilio_Helper</class>
        </Jurgis_Twilio>
      </helpers>
      <models>
        <Jurgis_Twilio>
                  <class>Jurgis_Twilio_Model</class>
        </Jurgis_Twilio>
      </models>
    </global>

app\code\local\Jurgis\Twilio\Model\Language.php

<?php
class Jurgis_Twilio_Model_Language
{
    public function toOptionArray()
    {
      return array(
            array(
                'value' => 'key1',
                'label' => 'Value 1',
            ),
            array(
                'value' => 'key2',
                'label' => 'Value 2',
            ),
        );
    }
}

When I go to my admin config, I get the error:

Fatal error: Call to a member function toOptionArray() on boolean in ...\app\code\core\Mage\Adminhtml\Block\System\Config\Form.php on line 463

Answer 1

change this

 <source_model>Twilio/Language</source_model>

to this

 <source_model>Jurgis_Twilio/Language</source_model>