mpdf pre/list style bug

test.php

<?php                                                                                                                   
                                                                                                                        
$html = '                                                                                                               
    <pre style="border: 2px solid #ff0000">test outside list</pre>                                                      
    <ul>                                                                                                                
        <li>                                                                                                            
            a pre<br />                                                                                                 
            <pre style="border: 2px solid #ff0000">test inside list</pre>                                               
        </li>                                                                                                           
    </ul>                                                                                                               
';                                                                                                                      
include("mpdf/mpdf.php");                                                                                               
$mpdf=new mPDF();                                                                                                       
$mpdf->WriteHTML($html);                                                                                                
$mpdf->Output();                                                                                                        
exit;