Ticket #33816: 33816.2.diff

src/wp-admin/includes/misc.php

@@ -246 +246 @@
         if ( defined( "WP_INSTALLING" ) )
                 return;
 
-        // If home changed, write rewrite rules to new location.
-        flush_rewrite_rules();
+        if ( is_multisite() && ms_is_switched() ) {
+                delete_option( 'rewrite_rules' );
+        } else {
+                flush_rewrite_rules();
+        }
 }
 
 /**