Object oriented programming, add_action in constructor not firing

I am trying to write a class that adds an action to the save_post hook, but the post_updated function never gets called. I tried some variations, but it never gets called. Am I doing something wrong?

class automatic_forwarder {
 function __construct() {
     add_action( 'save_post', array( $this, 'post_updated' ) );
 }

 function post_updated() {
     echo "Working";
 }
}