Radios select in form dont have unique wrapper class

When creating a form with radios as an input the "input" HTML tag is assigned a unique id, however the divs surrounding each pair of input and label tags are all assigned identical classes ("form-item form-type-radio form-item-extension-settings-region" in the code below). I would like to see these wrapper divs assigned an unique class so they are selectable with CSS.

The output of my form is as follows:

<label for="edit-extension-settings-region">
  Current Site Region <span class="form-required" title="This field is required.">*</span>
</label>
<div id="edit-extension-settings-region" class="form-radios">
  <div class="form-item form-type-radio form-item-extension-settings-region">
    <input id="edit-extension-settings-region-1" name="extension_settings_region" value="1" checked="checked" class="form-radio" type="radio">
    <label class="option" for="edit-extension-settings-region-1">
      <span class="radio-label">North West</span>
    </label>
  </div>
  <div class="form-item form-type-radio form-item-extension-settings-region">
    <input id="edit-extension-settings-region-2" name="extension_settings_region" value="2" class="form-radio" type="radio">
    <label class="option" for="edit-extension-settings-region-2">
      <span class="radio-label">North Central</span>
    </label>
  </div>
  <div class="form-item form-type-radio form-item-extension-settings-region">
    <input id="edit-extension-settings-region-3" name="extension_settings_region" value="3" class="form-radio" type="radio">
    <label class="option" for="edit-extension-settings-region-3">
      <span class="radio-label">North East</span>
    </label>
  </div>
  <div class="form-item form-type-radio form-item-extension-settings-region">
    <input id="edit-extension-settings-region-4" name="extension_settings_region" value="4" class="form-radio" type="radio">
    <label class="option" for="edit-extension-settings-region-4">
      <span class="radio-label">South West</span>
    </label>
  </div>
  <div class="form-item form-type-radio form-item-extension-settings-region">
    <input id="edit-extension-settings-region-5" name="extension_settings_region" value="5" class="form-radio" type="radio">
    <label class="option" for="edit-extension-settings-region-5">
      <span class="radio-label">South Central</span>
    </label>
  </div>
  <div class="form-item form-type-radio form-item-extension-settings-region">
    <input id="edit-extension-settings-region-6" name="extension_settings_region" value="6" class="form-radio" type="radio">
    <label class="option" for="edit-extension-settings-region-6">
      <span class="radio-label">South East</span>
    </label>
  </div>
</div>
<div class="description">Select the geographical region of the current website.</div>