diff --git a/IkiWiki/Plugin/openid.pm b/IkiWiki/Plugin/openid.pm
index 57cb139ca..f4ba8db18 100644
--- a/IkiWiki/Plugin/openid.pm
+++ b/IkiWiki/Plugin/openid.pm
@@ -42,7 +42,7 @@ sub getsetup () {
 		},
 		openid_realm => {
 			type => "string",
-			description => "url of openid realm (default is cgiurl)",
+			description => "url pattern of openid realm (default is cgiurl)",
 			safe => 0,
 			rebuild => 0,
 		},
diff --git a/doc/plugins/openid.mdwn b/doc/plugins/openid.mdwn
index 3fb4c26b8..f3b3abfbb 100644
--- a/doc/plugins/openid.mdwn
+++ b/doc/plugins/openid.mdwn
@@ -23,7 +23,8 @@ certian setups.
   It defaults to the `cgiurl` (or `openid_cgiurl` if set); only allowing
   ikiwiki's [[CGI]] to authenticate. If you have multiple ikiwiki instances,
   or other things using openid on the same site, you may choose to put them
-  all in the same realm to improve the user's openid experience.
+  all in the same realm to improve the user's openid experience. It is an
+  url pattern, so can be set to eg "http://*.example.com/"
 
 * `openid_cgiurl` can be used to cause a different than usual `cgiurl`
   to be used when doing openid authentication. The `openid_cgiurl` must