diff --git a/readme.md b/readme.md
index e3a042a..706516c 100644
--- a/readme.md
+++ b/readme.md
@@ -149,7 +149,7 @@ docker build -t prosody/xmpp .
 Next I recommend using a ```docker-compose.yml``` file:
 
 ```yaml
-version: '3.7'
+version: '3.9'
 
 services:
   server: