diff --git a/railties/guides/source/configuring.textile b/railties/guides/source/configuring.textile
index beb623757b..d91011c370 100644
--- a/railties/guides/source/configuring.textile
+++ b/railties/guides/source/configuring.textile
@@ -190,6 +190,7 @@ Every Rails application comes with a standard set of middleware which it uses in
 * +Rack::Runtime+ sets an +X-Runtime+ header, containing the time (in seconds) taken to execute the request.
 * +Rails::Rack::Logger+ notifies the logs that the request has began. After request is complete, flushes all the logs.
 * +ActionDispatch::ShowExceptions+ rescues any exception returned by the application and renders nice exception pages if the request is local or if +config.consider_all_requests_local+ is set to +true+. If +config.action_dispatch.show_exceptions+ is set to +false+, exceptions will be raised regardless.
+* +ActionDispatch::RequestId+ makes a unique X-Request-Id header available to the response and enables the +ActionDispatch::Request#uuid+ method.
 * +ActionDispatch::RemoteIp+ checks for IP spoofing attacks. Configurable with the +config.action_dispatch.ip_spoofing_check+ and +config.action_dispatch.trusted_proxies+ settings.
 * +Rack::Sendfile+ intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable with +config.action_dispatch.x_sendfile_header+.
 * +ActionDispatch::Callbacks+ runs the prepare callbacks before serving the request.