suprandr on "Contact Form 7 assign css to form elements"

Hello, Since I am working with a wordpress theme (Avada) I'd like to use theme styling for CF7 html elements. So my idea was to simply assign to the elements css classes, like that:

<p>[submit "Send" id:submit class:comment-submit ]</p>

However it seems that CF7 still applies the default classes. Any idea?

http://wordpress.org/extend/plugins/contact-form-7/