diff --git a/books/portable-docker.org b/books/portable-docker.org
index 87538850a..40fe75fb1 100644
--- a/books/portable-docker.org
+++ b/books/portable-docker.org
@@ -5557,9 +5557,16 @@ BACKUP_AWS_SECRET_ACCESS_KEY: Enter the S3 secret access key
 : OEuL3lMSdvdoFyVjEQTM4Trj/7VhHq7Q7cOFEpQPuxMHxsTVK3Hxne7st6Ty
 BACKUP_AWS_S3_PATH: Choose a directory inside the bucket (blank for root)
 : 
-
 #+end_stdout
 
+#+attr_shortcode: :style tip :title Tip
+#+begin_notice
+You should use a dedicated bucket for each backup instance, or you can
+share the same bucket between several instances, as long as you are
+careful to configure a unique =BACKUP_AWS_S3_PATH= sub-directory for
+each instance.
+#+end_notice
+
 You may optionally preserve an additional copy of the archive in a
 local volume: