SOLVED - Please help with Glossary character issue :(

I am using the Glossary module with Drupal 5. It seems to be working (applied the patch), but since our site is in cyrillic, the alphabet bar shows question marks. I found the following bit of code in the module file, which seems to be generating it, but I do not know what to substitute in the array directive (I need the Cyrillic alphabet there):

function _glossary_alphabar($vid, &$tree) {
  $blocks = array(range('0', '9'), range('a', 'z'));
  $vids = _glossary_get_filter_vids();
    
  $found_letters = array();
  foreach ($tree as $key=>$term) {
    if ($term->depth == 0) {
      $firstletter = strtolower($term->name[0]);
      if (! array_key_exists($firstletter, $found_letters)) {
        $found_letters[$firstletter] = 1;
        $tree[$key]->firstletter = $firstletter;
      }
    }
  }

I hope it is simple, but I am not into coding.