Reverse Not Found Error

If I have a URL Like this:

url(r'^reset/(?P<uid>\w+)/(?P<token>\w+)/$', 'django.contrib.auth.views.password_reset_confirm', name="reset_password")

and a URL tag like this:

{% url 'reset_password' uid=uid token=token %}

Why do I get this error when I try to render the page in which the tag is contained:

Reverse for 'reset_password' with arguments '()' and keyword arguments not found 

The both the uid and token are valid strings.