Simple Form (Master): :input_html class option gets added to container

simple_form_possible_bug_sample

After upgrading simple_form to current master, my design slightly broke because a class defined 
in :input_html options gets added to surrounding container. Is that desired behaviour? I'm using 
the wrapper sample options for Twitter Bootstrap: 
https://github.com/rafaelfranca/simple_form-bootstrap/blob/master/config/initializers/simple_form.rb

Example (haml):

= simple_form_for @company_profile,  wrapper: :inline, url: company_profile_path  
  = f.input :zipcode, label: t('common.zipcode'), input_html: {class: 'span2', 'data-xxx' => true}

Resulting HTML:

 <form accept-charset="UTF-8" action="/company_profile" class="simple_form edit_company_profile" data-remote="true" id="edit_company_profile_1" method="post" novalidate="novalidate">
  <div style="margin:0;padding:0;display:inline">
    <input name="utf8" type="hidden" value="&#x2713;" />
    <input name="_method" type="hidden" value="put" />
    <input name="authenticity_token" type="hidden" value="qUrINhA5ZTBcDWzoIV5qyLFK/iJO5z5t3YQtdZBbNIA=" />
   </div>
   <div class="clearfix string optional span2">
     <label class="string optional  " for="company_profile_zipcode">Zip Code </label>
     <div class="input">
        <input class="string optional span2" data-xxx="true" id="company_profile_zipcode" name="company_profile[zipcode]" size="50" type="text" value="40549" />
     </div>
   </div>
</form>

The class span2 gets added to the clearfix container div, but IMHO should only be 
added to the input field?

Or is that a desired change in behaviour? Other attributes specified in input_html 
are only added to the input-tag.