diff --git a/router/doc/tunnel.html b/router/doc/tunnel.html
index 809594ca6..f02473785 100644
--- a/router/doc/tunnel.html
+++ b/router/doc/tunnel.html
@@ -1,3 +1,4 @@
+<code>$Id$</code>
 <pre>
 1) <a href="#tunnel.overview">Tunnel overview</a>
 2) <a href="#tunnel.operation">Tunnel operation</a>