Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 6377)
+++ wp-includes/functions.php	(working copy)
@@ -863,6 +863,12 @@
 
 	$hook = 'do_feed_' . $feed;
 	do_action( $hook, $wp_query->is_comment_feed );
+	if(has_action($hook)) { 
+		do_action( $hook, $wp_query->is_comment_feed ); 
+	} else {
+		$message = sprintf( __( 'ERROR: %s is not a valid feed template' ), wp_specialchars($feed));
+		wp_die($message);
+	}
 }