diff --git a/wp-includes/ms-functions.php b/wp-includes/ms-functions.php
index ee385c70e3..5f3f15ed8b 100644
--- a/wp-includes/ms-functions.php
+++ b/wp-includes/ms-functions.php
@@ -308,7 +308,7 @@ function switch_to_blog( $new_blog ) {
 	if ( is_object( $current_user ) )
 		$current_user->_init_caps();
 
-	if ( is_object( $wp_object_cache ) )
+	if ( is_object( $wp_object_cache ) && isset( $wp_object_cache->global_groups ) )
 		$global_groups = $wp_object_cache->global_groups;
 	else
 		$global_groups = false;
@@ -361,7 +361,7 @@ function restore_current_blog() {
 	if ( is_object( $current_user ) )
 		$current_user->_init_caps();
 
-	if ( is_object( $wp_object_cache ) )
+	if ( is_object( $wp_object_cache ) && isset( $wp_object_cache->global_groups ) )
 		$global_groups = $wp_object_cache->global_groups;
 	else
 		$global_groups = false;
diff --git a/wp-includes/ms-load.php b/wp-includes/ms-load.php
index efdcb96b53..11b4ffa48c 100644
--- a/wp-includes/ms-load.php
+++ b/wp-includes/ms-load.php
@@ -17,7 +17,7 @@ if( defined( 'SUNRISE' ) )
 $wpdb->blogid           = $current_blog->blog_id;
 $wpdb->siteid           = $current_blog->site_id;
 $wpdb->set_prefix($table_prefix); // set up blog tables
-$table_prefix = $table_prefix . $blog_id . '_';
+$table_prefix = $wpdb->get_blog_prefix();
 
 // Fix empty PHP_SELF
 $PHP_SELF = $_SERVER['PHP_SELF'];