child_of not working with wp_list_categories

Hi all,

I have a list of categories that includes several sub-categories in the tree. When I use the wp_list_categories function to print these out, this works perfectly. However, when I add the child_of paramter and pass it a number of the category it just returns ‘No categories.’

$args = array(
     'child_of' => 5,
     'hide_empty' => 0
 );

wp_list_categories($args);

This returns ‘No categories’. But, if I just do:

wp_list_categories();

with no arguments, it prints out the tree correctly! Anyone know what I’m doing wrong?

Thanks!