Index: wp-includes/ms-default-filters.php
===================================================================
--- wp-includes/ms-default-filters.php	(revision 15125)
+++ wp-includes/ms-default-filters.php	(working copy)
@@ -29,7 +29,6 @@
 add_action( 'signup_hidden_fields', 'signup_nonce_fields' );
 
 // Template
-add_action( 'template_redirect', 'maybe_redirect_404' );
 add_filter( 'allowed_redirect_hosts', 'redirect_this_site' );
 
 // Administration
Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 15125)
+++ wp-includes/ms-functions.php	(working copy)
@@ -1308,16 +1308,6 @@
 	return $result;
 }
 
-function maybe_redirect_404() {
-	global $current_site;
-	if ( is_main_site() && is_404() && defined( 'NOBLOGREDIRECT' ) && ( $destination = apply_filters( 'blog_redirect_404', NOBLOGREDIRECT ) ) ) {
-		if ( $destination == '%siteurl%' )
-			$destination = network_home_url();
-		wp_redirect( $destination );
-		exit();
-	}
-}
-
 function maybe_add_existing_user_to_blog() {
 	if ( false === strpos( $_SERVER[ 'REQUEST_URI' ], '/newbloguser/' ) )
 		return false;