diff --git a/README.md b/README.md
index 8632ed8..ac3fdfa 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ ovh:
   consumer_key: str
   endpoint: str
 zone: str; example: redxef.at
-subdomain: str; example: subdomain-xyz
+subdomain: *Optional* str; example: subdomain-xyz
 field_type: *Optional* str; example: 'A' or 'AAAA'
 logging: *Optional*
   level: *Optional* str; default: :WARNING,ovhdns:INFO