WordPress add body class if page template

wordpress_page_template_body_class.php

<?php
  /**
   * Add a custom body class for a specific page template
   * Add the following to your theme functions.php file.
   */
  add_filter( 'body_class', 'custom_class' );
  function custom_class( $classes ) {
    if ( is_page_template( 'templates/page-contact.php' ) ) {
      $classes[] = 'contact';	
    }
  return $classes;
  }
?>