CodeIgniter helper not loading

I was trying to use this helper to create a country drop down list.(https://github.com/EllisLab/CodeIgniter/wiki/helper-dropdown-country-code)

I created a file called country_helper.php with the helper code inside, in my controller I'm loading that helper with $this->load->helper('country_helper');

But when using country_dropdown(); I'm getting the following error:

Call to undefined function country_dropdown() in /Users/wouter/Sites/socialagent.me/application/controllers/user.php on line 299

class Welcome extends CI_Controller {
    public function __construct()
    {   
        parent::__construct();
        $this->load->helper('country_helper');
        echo country_dropdown();
    }   
    public function index()
    {
    }    
}

I tried this code, and it works fine.