diff --git a/wp-includes/load.php b/wp-includes/load.php
index b086ff7d6..c15a9b6b8 100644
--- a/wp-includes/load.php
+++ b/wp-includes/load.php
@@ -318,13 +318,15 @@ function wp_set_wpdb_vars() {
  * @since 3.0.0
  */
 function wp_start_object_cache() {
-	global $_wp_using_ext_object_cache;
-	if ( file_exists( WP_CONTENT_DIR . '/object-cache.php' ) ) {
-		require_once ( WP_CONTENT_DIR . '/object-cache.php' );
-		$_wp_using_ext_object_cache = true;
-	} else {
-		require_once ( ABSPATH . WPINC . '/cache.php' );
-		$_wp_using_ext_object_cache = false;
+	if ( ! function_exists( 'wp_cache_init' ) ) {
+		global $_wp_using_ext_object_cache;
+		if ( file_exists( WP_CONTENT_DIR . '/object-cache.php' ) ) {
+			require_once ( WP_CONTENT_DIR . '/object-cache.php' );
+			$_wp_using_ext_object_cache = true;
+		} else {
+			require_once ( ABSPATH . WPINC . '/cache.php' );
+			$_wp_using_ext_object_cache = false;
+		}
 	}
 
 	wp_cache_init();
diff --git a/wp-includes/ms-settings.php b/wp-includes/ms-settings.php
index e3be06ccd..9a0dc34ed 100644
--- a/wp-includes/ms-settings.php
+++ b/wp-includes/ms-settings.php
@@ -152,11 +152,8 @@ $PHP_SELF = $_SERVER['PHP_SELF'];
 if ( empty($PHP_SELF) || ( empty($PHP_SELF) && !is_subdomain_install() && $current_blog->path != '/' ) )
 	$_SERVER['PHP_SELF'] = $PHP_SELF = preg_replace("/(\?.*)?$/",'',$_SERVER["REQUEST_URI"]);
 
-wp_cache_init(); // need to init cache again after blog_id is set
-if ( function_exists('wp_cache_add_global_groups') ) { // need to add these again. Yes, it's an ugly hack
-	wp_cache_add_global_groups(array ('users', 'userlogins', 'usermeta', 'site-options', 'site-lookup', 'blog-lookup', 'blog-details', 'rss'));
-	wp_cache_add_non_persistent_groups(array( 'comment', 'counts', 'plugins' ));
-}
+// need to init cache again after blog_id is set
+wp_start_object_cache();
 
 ms_default_constants( 'uploads' );