Style categories when displaying a post

Hi,
I wonder if anyone can help.
I am putting together a WP site and creating a theme from scratch for it.
I am using CSS to style my category li items as generated by wp_list_categories. When I click on a category name in the list, the html that gets generated that lists all posts in the category has class=”current-cat” – so I can write some CSS like:
li.current-cat a {font-weight: bold; }
to ‘bold’ the current category.

However, when I click on a post, the rendered page does not have the li item for the containing category as having the class=”current-cat” attribute; so the containing category for the displayed post is not bolded.

Does this make sense ? Has anyone managed to do this or similar ?

Cheers

JD