diff --git a/etc/emqx.conf b/etc/emqx.conf
index 82ec0dc8c..1479a18d2 100644
--- a/etc/emqx.conf
+++ b/etc/emqx.conf
@@ -925,12 +925,6 @@ listener.tcp.external.access.1 = allow all
 ## Value: Duration
 ## listener.tcp.external.proxy_protocol_timeout = 3s
 
-## Enable the option for X.509 certificate based authentication.
-## EMQX will use the common name of certificate as MQTT username.
-##
-## Value: cn | dn | crt
-## listener.tcp.external.peer_cert_as_username = cn
-
 ## The TCP backlog defines the maximum length that the queue of pending
 ## connections can grow to.
 ##
@@ -1886,7 +1880,9 @@ plugins.etc_dir = {{ platform_etc_dir }}/plugins/
 ## Value: File
 plugins.loaded_file = {{ platform_data_dir }}/loaded_plugins
 
-## File to store loaded plugin names.
+## The directory of extension plugins.
+##
+## Value: File
 plugins.expand_plugins_dir = {{ platform_plugins_dir }}/
 
 ##--------------------------------------------------------------------