2 files changed, 7 insertions, 5 deletions
diff --git a/actionpack/lib/action_controller/metal/mime_responds.rb b/actionpack/lib/action_controller/metal/mime_responds.rb
index e62da0fa70..88a4818c16 100644
--- a/actionpack/lib/action_controller/metal/mime_responds.rb
+++ b/actionpack/lib/action_controller/metal/mime_responds.rb
@@ -191,7 +191,7 @@ module ActionController #:nodoc:
 
       if format = collector.negotiate_format(request)
         _process_format(format)
-        _set_content_type _get_content_type format
+        _set_rendered_content_type format
         response = collector.response
         response ? response.call : render({})
       else
diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index 363d45c722..4214399b6f 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -56,12 +56,14 @@ module ActionController
       nil
     end
 
-    def _get_content_type(rendered_format)
-      self.content_type || rendered_format.to_s
+    def _set_html_content_type
+      self.content_type = Mime::HTML.to_s
     end
 
-    def _set_content_type(format)
-      self.content_type = format
+    def _set_rendered_content_type(format)
+      unless response.content_type
+        self.content_type = format.to_s
+      end
     end
 
     # Normalize arguments by catching blocks and setting them on :update.