WP_Query says "Call to a member function have_posts() on a non-object"

Hi,

I have this weird error when trying to make a simple WP_Query. Maybe there is something evident that I am missing but I can’t see it.. Here is my code, it is all there is in the page, beside header.php and footer.php obviously..

// Black Boxes (there is 2)
  $pages = new WP_Query(
    array(
      'post_type' => 'page',
      'post__in'  => array( 23, 21 )
    )
  );

  if ( ! $pages->have_posts() ) :
  endif;

  while( $pages->have_posts() ) : $pages->the_post();
    the_title();
  endwhile;

  // Prevent weirdness
  wp_reset_query();

Thanks!