1 files changed, 9 insertions, 2 deletions
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index edb522ff49..b9db7a4508 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -162,8 +162,15 @@ module ActionDispatch # :nodoc:
     end
 
     def assign_default_content_type_and_charset!
-      self.content_type ||= Mime::HTML
-      self.charset ||= default_charset unless sending_file?
+      if type = headers['Content-Type'] || headers['type']
+        unless type =~ /charset=/ || sending_file?
+          headers['Content-Type'] = "#{type}; charset=#{default_charset}"
+        end
+      else
+        type = Mime::HTML.to_s
+        type += "; charset=#{default_charset}" unless sending_file?
+        headers['Content-Type'] = type
+      end
     end
 
     def prepare!