Can I add a category to a custom post type automatically?

Hi,

I’m trying to add a normal category to a custom post type automatically.

This is my code:

add_action('init', 'myfunc_reg');

function myfunc_reg() {

	$labels = array(
		stuff
	);

	$args = array(
		more stuff,
        'taxonomies' => array('category')
	  ); 

  register_taxonomy_for_object_type('category', 'my_category');
	register_post_type( 'specials' , $args );
}

When I add a new entry for this custom post type I see the categories-selection at the right side. But there is no preselection with “my_category”.

Is it possible to set this value when I write a new entry automatically (not manually which I have to do at the moment)?