diff --git a/railties/guides/source/rails_on_rack.textile b/railties/guides/source/rails_on_rack.textile
index d6cbd84b1f9091b9b621643de4875a9df4e06793..9526526bc70b31f454005377a9a84b13c6f619c7 100644
--- a/railties/guides/source/rails_on_rack.textile
+++ b/railties/guides/source/rails_on_rack.textile
@@ -95,6 +95,7 @@ use ActiveSupport::Cache::Strategy::LocalCache
 use Rack::Runtime
 use Rails::Rack::Logger
 use ActionDispatch::ShowExceptions
+use ActionDispatch::DebugExceptions
 use ActionDispatch::RemoteIp
 use Rack::Sendfile
 use ActionDispatch::Callbacks