update_option fails after switching blog

hi,

I’ve a wordpress multisite environment and in the functions.php of the primary blog I setup this action, that will run after a brand new blog is created.

function register_new_blog_option($blog_id, $user_id, $domain, $path, $site_id, $meta)
{
  switch_to_blog($blog_id);
  update_option('hw_option', 'hello word!');//fails to store into blog_id
  restore_current_blog();

  //this works and store value in wp_options
  update_option('hw_option', 'hello word!');
}
add_action('wpmu_new_blog','register_new_blog_option', 10, 6);

But it doesn’t work.
The action is executed but the option is not stored.
Even if I use update_blog_option it fails.
It seems like the switch_to_blog function fails or something goes wrong.

Any ideas or am I missing something?
Thank you very much in advance.