diff --git a/lib/octopress-codefence.rb b/lib/octopress-codefence.rb
index 2a8e814..21ecdf8 100644
--- a/lib/octopress-codefence.rb
+++ b/lib/octopress-codefence.rb
@@ -5,7 +5,7 @@ module Octopress
   module Codefence
     Jekyll::Hooks.register [:posts, :pages, :documents], :pre_render do |item, payload|
       if item.respond_to?(:ext)
-        ext = item.ext
+        ext = item.data['ext']
       else
         ext = nil
       end
@@ -17,7 +17,7 @@ class Highlighter
       LangCaption = /([^\s]+)\s*(.+)?/i
 
       def initialize(input, ext=nil, aliases=nil)
-        @input   = input
+        @input   = input.dup
         @ext     = ext
         @aliases = aliases
       end