How can I concatenate forloop.counter to a string in my django template

I am already trying to concatenate like this:

{% for choice in choice_dict %}
    {% if choice =='2' %}
        {% with "mod"|add:forloop.counter|add:".html" as template %}
            {% include template %}
        {% endwith %}                   
    {% endif %}
{% endfor %}    

but for some reason I am only getting "mod.html" and not the forloop.counter number. Does anyone have any idea what is going on and what I can do to fix this issue? Thanks alot!