diff --git a/Linux-and-BSD-firewalls-cheat-sheet.adoc b/Linux-and-BSD-firewalls-cheat-sheet.adoc
index 3ccaf7b..bc6687d 100644
--- a/Linux-and-BSD-firewalls-cheat-sheet.adoc
+++ b/Linux-and-BSD-firewalls-cheat-sheet.adoc
@@ -32,7 +32,7 @@ v1.0, 2020-09-01
 |List all zones with their rules and associated interfaces.
 
 |*firewall-cmd -add-service <service name>*
-|Add predefined service by name to the default zone, with action ACCEPT.
+|Add predefined service by name to the default zone, with action ACCEPT, e.g. `firewall-cmd -add-service ftp` .
 
 
 |===