diff --git a/MANIFEST b/MANIFEST
index 5a1b16361d..3d5b887988 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -255,6 +255,7 @@ lib/thread.rb
 lib/thwait.rb
 lib/time.rb
 lib/timeout.rb
+lib/tmpdir.rb
 lib/tracer.rb
 lib/tsort.rb
 lib/uri.rb