diff --git a/includes/core-phpunit/includes/install.php b/includes/core-phpunit/includes/install.php
index 8a595903c..4d39db759 100644
--- a/includes/core-phpunit/includes/install.php
+++ b/includes/core-phpunit/includes/install.php
@@ -40,7 +40,16 @@
 require_once ABSPATH . 'wp-settings.php';
 
 require_once ABSPATH . 'wp-admin/includes/upgrade.php';
-require_once ABSPATH . 'wp-includes/class-wpdb.php';
+
+/**
+ * File was renamed in WordPress 6.1.
+ *
+ * @see https://core.trac.wordpress.org/ticket/56268
+ * @see https://github.com/WordPress/WordPress/commit/8484c7babb6b6ee951f83babea656a294157665d
+ */
+require_once file_exists( ABSPATH . 'wp-includes/class-wpdb.php' )
+    ? ABSPATH . 'wp-includes/class-wpdb.php'
+    : ABSPATH . 'wp-includes/wp-db.php';
 
 // Override the PHPMailer.
 global $phpmailer;