WordPress – Custom Post Type permalink collision

I use WordPress with Custom Post Types and Custom Taxonomies.

Problem

I try to create a post with the path /nyheter/bolag/post/ but it gets redirected to /bolag/post/. It’s because I have a Custom Post Type with the slug bolag and WP probably try to correct the path.

How is this solved? Code, plugins?

Code placed in functions.php

<?php
add_action( 'init', 'create_post_type' );
add_action( 'init', 'register_taxonomies' );

function create_post_type() {
$args_bolag = array(
    'labels' => array(
        'name' => 'Bolag',
        'singular_name' => 'Bolag'
    ),
    'public' => true,
    'has_archive' => true,
    'rewrite' => array('slug' => 'bolag'),
);

$args_nyheter = array(
    'labels' => array(
        'name' => 'Nyheter',
        'singular_name' => 'Nyheter'
    ),
    'public' => true,
    'has_archive' => true,
    'rewrite' => array('slug' => 'nyheter'),
);

register_post_type( 'bolag', $args_bolag );
register_post_type( 'nyheter', $args_nyheter );
}

function register_taxonomies()
{
$args_firma = array(
    'label' => __( 'Firma' ),
    'rewrite' => array( 'slug' => 'nyheter/bolag' ),
    'hierarchical' => true,
);
register_taxonomy( 'firma', 'nyheter', $args_firma );
}