diff --git a/wp-admin/upgrade.php b/wp-admin/upgrade.php
index 251513a18d..5b1eec45e0 100644
--- a/wp-admin/upgrade.php
+++ b/wp-admin/upgrade.php
@@ -6,14 +6,6 @@
  * @subpackage Administration
  */
 
-/**
- * We are upgrading WordPress.
- *
- * @since 1.5.1
- * @var bool
- */
-define( 'WP_INSTALLING', true );
-
 /** Load WordPress Bootstrap */
 require( '../wp-load.php' );