How to add class attribute to select tag in rails 3

I want to add class attribute to select tag in rails 3 my code is

<div >
    <%= f.label :type %><br />
    <%= f.select "type_id", options_from_collection_for_select(@type,
    "type_id","name"),:include_blank=>true%>

</div>

My problem is that I want to add one specific class name to this select tag for validation purpose. I tried adding

  :class=>"myclassname"

but it not worked for me.plz resolve my issue