diff --git a/actionpack/Rakefile b/actionpack/Rakefile
index 86f7adaee3..684b828254 100644
--- a/actionpack/Rakefile
+++ b/actionpack/Rakefile
@@ -58,11 +58,12 @@ end
 desc 'Old Controller Tests on New Base'
 Rake::TestTask.new(:test_new_base_on_old_tests) do |t|
   t.libs << "test/new_base" << "test"
-  # content_type layout
+  # layout
   # Dir.glob( "test/{dispatch,template}/**/*_test.rb" ).sort +
   t.test_files = %w(
-    addresses_render base benchmark caching capture dispatcher flash mime_responds
-    record_identifier redirect render rescue url_rewriter webservice
+    addresses_render base benchmark caching capture content_type dispatcher
+    flash mime_responds record_identifier redirect render rescue url_rewriter
+    webservice
   ).map { |name| "test/controller/#{name}_test.rb" }
 end
 
diff --git a/actionpack/lib/action_controller/new_base/renderer.rb b/actionpack/lib/action_controller/new_base/renderer.rb
index 6176212970..81685ca9d6 100644
--- a/actionpack/lib/action_controller/new_base/renderer.rb
+++ b/actionpack/lib/action_controller/new_base/renderer.rb
@@ -38,7 +38,11 @@ module ActionController
       ret = super(options)
       
       options[:_template] ||= _action_view._partial
-      response.content_type ||= options[:_template].mime_type
+      response.content_type ||= begin
+        mime = options[:_template].mime_type
+        mime &&= mime.to_sym
+        formats.include?(mime) ? mime : formats.first
+      end
       ret
     end