diff --git a/resources/db/update/42.php b/resources/db/update/42.php
index <HASH>..<HASH> 100644
--- a/resources/db/update/42.php
+++ b/resources/db/update/42.php
@@ -1,5 +1,8 @@
 <?php
 
+// To be run in prod beforehand:
+// pt-online-schema-change --execute --charset=utf8 --user=root --ask-pass --database=skadate t=cm_user --alter='CHANGE `site` `site` int(10) unsigned DEFAULT NULL'
+
 if ('INT' !== CM_Db_Db::describeColumn('cm_user', 'site')->getType()) {
     CM_Db_Db::exec("ALTER TABLE `cm_user` CHANGE `site` `site` int(10) unsigned DEFAULT NULL;");
 }
Added Percona command for prod