Adding a class in check_box_tag

I search through the net and cannot find a way. So far, I have tried:

<%= check_box_tag "course[location_ids][]", location.id, class: 'checkbox-inline'%>

This will output:

input type: "checkbox" name="course[location_ids][] id="course_location_ids_" value="1" checked="checked"

For some reason, it makes a checked input.

<%= check_box_tag "course[location_ids][]", location.id, :class => 'checkbox-inline'%>

does the same as the first one

How do I add a class inside of a check_box_tag