diff --git a/tsa/howto/upgrades/buster.mdwn b/tsa/howto/upgrades/buster.mdwn
index bb6de53d18c59a2c6fdda90a58d14bb29e675540..5b178f7c5ae1f9fe45337a1b96b016a168585e9b 100644
--- a/tsa/howto/upgrades/buster.mdwn
+++ b/tsa/howto/upgrades/buster.mdwn
@@ -128,6 +128,10 @@ PostgreSQL is special and needs to be upgraded manually.
 
  3. do the actual cluster upgrade, on the database server:
 
+        export LC_ALL=C.UTF-8 &&
+        printf "about to drop cluster main on postgresql-11, press enter to continue" &&
+        read _ &&
+        pg_dropcluster --stop 11 main &&
         pg_upgradecluster -m upgrade -k &&
         for cluster in `ls /etc/postgresql/9.6/`; do
             mv /etc/postgresql/9.6/$cluster/conf.d/* /etc/postgresql/11/$cluster/conf.d/