diff --git a/lib/jekyll.rb b/lib/jekyll.rb
index e9f4547b..cee9905d 100644
--- a/lib/jekyll.rb
+++ b/lib/jekyll.rb
@@ -99,7 +99,7 @@ module Jekyll
     #
     # Returns the final configuration Hash.
     def configuration(override = {})
-      config = Configuration[Configuration::DEFAULTS]
+      config = Configuration[Marshal.load(Marshal.dump(Configuration::DEFAULTS))]
       override = Configuration[override].stringify_keys
       unless override.delete('skip_config_files')
         config = config.read_config_files(config.config_files(override))