Template does not recognize is_singular(‘product’)

I’d like to make a conditional modification (outside wpsc-single_product.php on the base page template) to be invoked only when wpsc-single_product.php is in use. However, I’m finding neither (is_singular(‘product’)) nor (is_page_template(‘wpsc-single_product.php’)) triggers the modification. Apparently, WP doesn’t know what template it’s using or that it’s displaying a custom post type single?

What do you suggest?