CSS 3 nth of type restricted to class

Is there a way to limit CSS 3's nth-of-type to a class? I've got a dynamic number of section elements with different classes designating their layout needs. I'd like to grab every third .module, but it seems that nth-of-type looks up classes element type and then calculates the type. Instead I'd like to limit it to only .modules.

JSFiddle to demonstrate: http://jsfiddle.net/danielredwood/e2BAq/1/

HTML:

<section class="featured video">
    <h1>VIDEO</h1>
</section>
<section class="featured module">
    <h1>NOT A VIDEO</h1>
</section>
<section class="featured module">
    <h1>NOT A VIDEO</h1>
</section>
<section class="featured module">
    <h1>NOT A VIDEO (3)</h1>
</section>
<section class="featured module">
    <h1>NOT A VIDEO</h1>
</section>
<section class="featured module">
    <h1>NOT A VIDEO</h1>
</section>
<section class="featured module">
    <h1>NOT A VIDEO (6)</h1>
</section>

​CSS:

.featured {
  width: 31%;
  margin: 0 0 20px 0;
  padding: 0 3.5% 2em 0;
  float: left;
  background: #ccc;
}

.featured.module:nth-of-type(3n+3) {
  padding-right: 0;
  background: red;
}

.featured.video {
  width: auto;
  padding: 0 0 2em 0;
  float: none;
}​