Custom post type rewrite not working

I’m not sure what it’s wrong here. I’m registering a post type like:

register_post_type('post-type', array(
    [...]
    'rewrite' => array (
        'slug' => 'someslug',
        'with_front' => false
    )
);

But whenever I visit “http://webpage/someslug”, I get canonical redirected to a post with a title similar to “someslug”.

Tried to deactivate all plugins, reloaded the permalink options by saving it again, and other stuff…

Well, really appreciate any help.