FixedHeader autoWidth bug

HTML

<link rel="stylesheet" href="https://cdn.datatables.net/1.10.7/css/jquery.dataTables.css">
<script src="https://cdn.datatables.net/1.10.7/js/jquery.dataTables.js"></script>
<link rel="stylesheet" href="https://cdn.datatables.net/fixedheader/3.1.7/css/fixedHeader.dataTables.css">
<script src="https://cdn.datatables.net/fixedheader/3.1.7/js/dataTables.fixedHeader.js"></script>
<table id="test_table">
  <thead>
    <tr>
      <th>Sponsor name</th>
      <th>Tests</th>
      <th>Due tests</th>
      <th>Unreported</th>
      <th>% Reported</th>
    </tr>
  </thead>

  <tr><td> Foo corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Bar corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Humbug corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Moo corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Squeak corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Yap corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Howl corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Maeow corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Huggle corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Silent corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Silent corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Silent corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Silent corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Silent corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Silent corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
  <tr><td> Silent corp </td><td> 10 </td><td> 20 </td><td> 30 </td><td> 1% </td></tr>
</table>

JavaScript

var t = $('#test_table').DataTable({
  "fixedHeader": true,
  "paging": false,
  "autoWidth": false,
  "columns": [
    { "width": "200px" },
    { "width": "17.5%" },
    { "width": "17.5%" },
    { "width": "17.5%" },
    { "width": "17.5%" }
   ],
});