diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 5b15c5e..06365a6 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -571,6 +571,9 @@
 # applies to user and project (string value)
 #admin_domain_name = <None>
 
+# ID of the default domain (string value)
+#default_domain_id = default
+
 
 [identity-feature-enabled]