Index: lib/webrick/config.rb
===================================================================
--- lib/webrick/config.rb	(revision 35969)
+++ lib/webrick/config.rb	(working copy)
@@ -33,7 +33,7 @@ module WEBrick
       :StartCallback  => nil,
       :StopCallback   => nil,
       :AcceptCallback => nil,
-      :DoNotReverseLookup => nil,
+      :DoNotReverseLookup => true,
       :ShutdownSocketWithoutClose => false,
     }