Prevent replacing <input type=“submit”> with <button>

I am using Bootstrap 3 subtheme (7.x-3.1-beta2 ) on Drupal 7 for the administrative backend. It seems that the Bootstrap base theme replaces <input type="submit"> with a <button> element. That breaks the layout of the views backend.

I tried to change this by:

• copying button.func.php into the subtheme
• renaming the function according to the subtheme name
• modifying the output to return instead of

Code in button.func.php

<?php
function bootstrap_subtheme_adl_admin_button($variables) {
  $element = $variables['element'];
  $value = $element['#value'];
   if (!empty($element['#icon'])) {
     if ($element['#icon_position'] === 'before') {
       $value = $element['#icon'] . ' ' . $value;
     }
   elseif ($element['#icon_position'] === 'after') {
     $value .= ' ' . $element['#icon'];
    }
  }

return '<input' . drupal_attributes($element['#attributes']) . '>\n';
}

However, this does not have any visible effect. Any advise?