diff --git src/wp-admin/setup-config.php src/wp-admin/setup-config.php
index ddcb4943c7..b39c4458cd 100644
--- src/wp-admin/setup-config.php
+++ src/wp-admin/setup-config.php
@@ -123,6 +123,11 @@ if ( ! empty( $_REQUEST['language'] ) ) {
 	$language = $GLOBALS['wp_local_package'];
 }
 
+/**
+ * @global wpdb $wpdb WordPress database abstraction object.
+ */
+global $wpdb;
+
 switch ( $step ) {
 	case -1:
 		if ( wp_can_install_language_pack() && empty( $language ) ) {