diff --git a/config/jail.conf b/config/jail.conf
index b0ed6355..f545ff13 100644
--- a/config/jail.conf
+++ b/config/jail.conf
@@ -771,7 +771,7 @@ maxretry = 1
 [pass2allow-ftp]
 # this pass2allow example allows FTP traffic after successful HTTP authentication
 port         = ftp,ftp-data,ftps,ftps-data
-# knocking URL needs to be customized in apache-pass.local
+# knocking_url variable must be overridden to some secret value in filter.d/apache-pass.local
 filter       = apache-pass
 # access log of the website with HTTP auth
 logpath      = %(apache_access_log)s