1 files changed, 9 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/http/mime_negotiation.rb b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
index 7acf91902d..004713ec1a 100644
--- a/actionpack/lib/action_dispatch/http/mime_negotiation.rb
+++ b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
@@ -67,6 +67,8 @@ module ActionDispatch
 
           v = if params_readable
             Array(Mime[parameters[:format]])
+          elsif format_from_path_extension
+            [Mime[format_from_path_extension]]
           elsif use_accept_header && valid_accept_header
             accepts
           elsif xhr?
@@ -160,6 +162,13 @@ module ActionDispatch
       def use_accept_header
         !self.class.ignore_accept_header
       end
+
+      def format_from_path_extension
+        path = @env['action_dispatch.original_path'] || @env['PATH_INFO']
+        if match = path && path.match(/\.(\w+)\z/)
+          match.captures.first
+        end
+      end
     end
   end
 end