diff --git a/lib/tmpdir.rb b/lib/tmpdir.rb
index 0aa9cf5e3b..fafe120b3e 100644
--- a/lib/tmpdir.rb
+++ b/lib/tmpdir.rb
@@ -111,7 +111,7 @@ class Dir
     end
   end
 
-  module Tmpname
+  module Tmpname # :nodoc:
     module_function
 
     def tmpdir