diff --git a/doc/dhcp-to-dns.md b/doc/dhcp-to-dns.md
index 9f8cb8b..0c112b3 100644
--- a/doc/dhcp-to-dns.md
+++ b/doc/dhcp-to-dns.md
@@ -33,6 +33,7 @@ The configuration goes to `global-config-overlay`, these are the parameters:
 
 * `Domain`: the domain used for dns records
 * `HostNameInZone`: whether or not to add the dhcp/dns server's hostname
+* `PrefixInZone`: whether or not to add prefix `dhcp`
 
 See also
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