Index: wp-admin/network/admin.php
===================================================================
--- wp-admin/network/admin.php	(revision 17488)
+++ wp-admin/network/admin.php	(working copy)
@@ -15,7 +15,7 @@
 if ( ! is_multisite() )
 	wp_die( __( 'Multisite support is not enabled.' ) );
 
-if ( ! is_main_site() ) {
+if ( ( $current_blog->domain != $current_site->domain ) || ( $current_blog->path != $current_site->path ) ) {
 	wp_redirect( network_admin_url() );
 	exit;
 }
Index: wp-admin/user/admin.php
===================================================================
--- wp-admin/user/admin.php	(revision 17488)
+++ wp-admin/user/admin.php	(working copy)
@@ -16,7 +16,7 @@
 	exit;
 }
 
-if ( ! is_main_site() ) {
+if ( ( $current_blog->domain != $current_site->domain ) || ( $current_blog->path != $current_site->path ) ) {
 	wp_redirect( user_admin_url() );
 	exit;
 }