diff --git a/upgrade-guides/upgrade-to-21.0.9.12.md b/upgrade-guides/upgrade-to-21.0.9.12.md
index f3b1f28ef8dd6e21001d1ef2bdddb971acf4ff7e..98f3a332d438e4573565eab3a0d7f3b7a106f807 100644
--- a/upgrade-guides/upgrade-to-21.0.9.12.md
+++ b/upgrade-guides/upgrade-to-21.0.9.12.md
@@ -1,5 +1,9 @@
 # To upgrade from ecloud 20.x.x.x to 21.0.9.12
 
+- As usual, upgrade your OS with latest patchs, optionally take backup/snapshot
+
+  - NB: you may want to filter out incomming email (TCP 25 & 587) during this upgrade, to avoid losing any messages in case of a rollback
+
 - In your `docker-compose.yml` file update the following:
   - Set the redis image to `redis:6.2-alpine`
   - Set the welcome image to `registry.gitlab.e.foundation/e/infra/docker-welcome:2.5.0`
@@ -35,5 +39,12 @@
 
 - Run `docker-compose pull`
 - Run `docker-compose up -d`
+
+- Examine `docker-compose logs --tail=500 nextcloud` for the following messages:
+  - `nextcloud       | Upgrading nextcloud from x.x.x.x ...` (x.x.x.x is your previous Nextcloud version)
+  - `nextcloud       | Update successful`
+
 - Enable the `ecloud-accounts` app:
-  `docker exec -u www-data nextcloud /var/www/html/occ app:enable ecloud-accounts`
\ No newline at end of file
+  `docker exec -u www-data nextcloud /var/www/html/occ app:enable ecloud-accounts`
+
+- Run `docker exec -T --user www-data nextcloud php occ db:add-missing-indices`