diff --git a/matrix/coturn/README.md b/matrix/coturn/README.md
index 965b7c9..98bd94f 100644
--- a/matrix/coturn/README.md
+++ b/matrix/coturn/README.md
@@ -160,3 +160,5 @@ renew_hook = /etc/coturn/fixssl
 
 Yes, it's a bit primitive and could (should?) be polished. But for now: it
 works.
+
+Be sure to open the correct ports in the [firewall](../firewall).