WP_Query: Orderby custom fields

wp_query-orderby-meta-1.php

<?php

$args = array(
  'post_type' => 'custom_post_name' // including the post type name seems to make this not work!
  'meta_key' => 'custom_field_name',
  'orderby' => 'meta_value',
  'order' => 'ASC',
  'tax_query' => array(
    array(
      'taxonomy' => 'custom_tax_name',
      'field' => 'term_id',
      'terms' => array( 1, 2, 3 ),
    ),
  ),
);
$query = new WP_Query( $args );

wp_query-orderby-meta-2.php

<?php

// leaving out the post_type parameter made it all good again
$args = array(
  'meta_key' => 'custom_field_name',
  'orderby' => 'meta_value',
  'order' => 'ASC',
  'tax_query' => array(
    array(
      'taxonomy' => 'custom_tax_name',
      'field' => 'term_id',
      'terms' => array( 1, 2, 3 ),
    ),
  ),
);
$query = new WP_Query( $args );