diff --git a/lib/stringsupport.rb b/lib/stringsupport.rb
index be97d61a..658283dd 100644
--- a/lib/stringsupport.rb
+++ b/lib/stringsupport.rb
@@ -41,7 +41,7 @@ end
 #--
 if "".respond_to?(:force_encoding)
   def purify
-    text = check_ncrs.as_utf8
+    text = self.dup.check_ncrs.as_utf8
     text.chars.collect{|c| c.as_bytes}.grep(UTF8_REGEX).join.as_utf8
   end
 else
diff --git a/lib/wiki_content.rb b/lib/wiki_content.rb
index 8825029f..2e3b6be4 100644
--- a/lib/wiki_content.rb
+++ b/lib/wiki_content.rb
@@ -7,6 +7,7 @@ require_dependency 'chunks/wiki'
 require_dependency 'chunks/literal'
 require 'chunks/nowiki'
 require 'sanitizer'
+require 'stringsupport'
 
 
 # Wiki content is just a string that can process itself with a chain of
@@ -189,6 +190,7 @@ class WikiContent < String
   def render!
     pre_render!
     @options[:engine].apply_to(self)
+    as_bytes
     # unmask in one go. $~[1] is the chunk id
     gsub!(MASK_RE[ACTIVE_CHUNKS]) do
       chunk = @chunks_by_id[$~[1].to_i]
@@ -200,6 +202,7 @@ class WikiContent < String
         chunk.unmask_text
       end
     end
+    as_utf8
     self.replace xhtml_sanitize(self)
   end