checkbox on Bootstrap 3 shows up incorrect in responsive layout

I've been using Bootstrap buttons to create checkboxes with images. When I directly use the code example, the buttons don't have a checkbox. But when I put them in a responsive layout, they have a checkbox.

I've created a JSFiddle that demonstrates this. Is there a way to have Bootstrap buttons without the checkbox itself?

Here's the code:

<div class="container-fluid">
  <div class="row">
  <div class="btn-group" data-toggle="buttons">
    <div class=".col-md-4">
      <label class="btn btn-primary">
        <input autocomplete="off" type="checkbox">
          Checkbox 1
        </input>
      </label>
    </div>
    <div class=".col-md-4">
      <label class="btn btn-primary">
        <input autocomplete="off" type="checkbox">
          Checkbox 2
        </input>
      </label>
    </div>
    <div class=".col-md-4">
      <label class="btn btn-primary">
        <input autocomplete="off" type="checkbox">
          Checkbox 3
        </input>
      </label>
    </div>
  </div>
</div>