diff --git a/src/wp-includes/load.php b/src/wp-includes/load.php
index a29eed1002..71b3a4a3e7 100644
--- a/src/wp-includes/load.php
+++ b/src/wp-includes/load.php
@@ -418,7 +418,12 @@ function require_wp_db() {
 		return;
 	}
 
-	$wpdb = new wpdb( DB_USER, DB_PASSWORD, DB_NAME, DB_HOST );
+	$dbuser     = defined( 'DB_USER' ) ? DB_USER : '';
+	$dbpassword = defined( 'DB_PASSWORD' ) ? DB_PASSWORD : '';
+	$dbname     = defined( 'DB_NAME' ) ? DB_NAME : '';
+	$dbhost     = defined( 'DB_HOST' ) ? DB_HOST : '';
+
+	$wpdb = new wpdb( $dbuser, $dbpassword, $dbname, $dbhost );
 }
 
 /**