Accessing a custom object with instanceof

I have instantiated a new object from a class in my app/libraries folder as such:

PHP Code:

// in controller
use App\Libraries\LN_Account; 


PHP Code:

// in controller method
$account = new LN_Account(); 


But when I pass $account to my model and check if it is an instance of LN_Account the conditional fails. 

PHP Code:

// in controller method
$account = $this->AuthenticationModel->getAuthenticationCredentials($account); 


PHP Code:

// in model
public function getAuthenticationCredentials($account) {
    if ($account instanceof LN_Account) {
         // I never get here
     }
} 


How do I make LN_Account visible to my model?