diff --git a/wp-activate.php b/wp-activate.php
index dcfee6a..eefe8e7 100644
--- a/wp-activate.php
+++ b/wp-activate.php
@@ -19,6 +19,7 @@ if ( !is_multisite() ) {
 	die();
 }
 
+global $wp_object_cache;
 if ( is_object( $wp_object_cache ) )
 	$wp_object_cache->cache_enabled = false;