diff --git a/wp-admin/ms-edit.php b/wp-admin/ms-edit.php
index 28a765ef1..910bc4987 100644
--- a/wp-admin/ms-edit.php
+++ b/wp-admin/ms-edit.php
@@ -219,7 +219,7 @@ switch ( $_GET['action'] ) {
 		}
 
 		// rewrite rules can't be flushed during switch to blog
-		update_option( 'rewrite_rules', '' );
+		delete_option( 'rewrite_rules' );
 
 		// update blogs table
 		$blog_data = stripslashes_deep($_POST[ 'blog' ]);