diff --git a/UPGRADING b/UPGRADING
index 935a12e03fde8..ef7df88cf829a 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -102,6 +102,10 @@ PHP 8.4 UPGRADE NOTES
   . The DSN's credentials, when set, are given priority over their PDO
     constructor counterparts, being closer to the documentation states.
 
+- MySQLnd
+  . The error code reported for MySQL server wait timeouts has been changed from 2006
+    to 4031 for MySQL server versions 8.0.24 and above.
+
 - PCNTL:
   . The functions pcntl_sigprocmask(), pcntl_sigwaitinfo() and
     pcntl_sigtimedwait() now throw: