Add post category to body class

// =========================================================================
// ADD POST CATEGORY TO BODY CLASS
// =========================================================================
function add_category_to_body_class( $classes ) {
	if ( !is_single() )
	return $classes;
	$post_categories = get_the_category();
		foreach( $post_categories as $current_category ) {
			$classes[] = 'category-' . $current_category->slug;
		}
	return $classes;
	}
add_filter( 'body_class', 'add_category_to_body_class' );