diff --git a/index.md b/index.md
index 3db591a..685df68 100644
--- a/index.md
+++ b/index.md
@@ -15,6 +15,7 @@ Setup chrony NTP.
   - [chrony_logdir](#chrony_logdir)
   - [chrony_ntsdumpdir](#chrony_ntsdumpdir)
   - [chrony_pool](#chrony_pool)
+  - [chrony_port](#chrony_port)
   - [chrony_server](#chrony_server)
 - [Dependencies](#dependencies)
 
@@ -65,6 +66,16 @@ chrony_ntsdumpdir: /var/lib/chrony
 chrony_pool: 2.pool.ntp.org iburst
 ```
 
+### chrony_port
+
+The port option can be set to 0 to make chrony daemon to never open any listening port for server operation and to operate strictly in a client-only mode.
+
+#### Default value
+
+```YAML
+chrony_port: 0
+```
+
 ### chrony_server
 
 #### Default value