Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 21542)
+++ wp-includes/post.php	(working copy)
@@ -985,8 +985,10 @@
 		'show_in_nav_menus' => null, 'show_in_menu' => null, 'show_in_admin_bar' => null,
 		'delete_with_user' => null,
 	);
-	$args = wp_parse_args($args, $defaults);
-	$args = (object) $args;
+	$args = wp_parse_args( $args, $defaults);
+	$args = (object) apply_filters( 'register_post_type_args', $args, $post_type );
+	if ( empty( $args ) )
+		return false;
 
 	$post_type = sanitize_key($post_type);
 	$args->name = $post_type;