diff --git a/actionpack/lib/action_controller/metal/mime_responds.rb b/actionpack/lib/action_controller/metal/mime_responds.rb
index 09aa76f1ca1ee139d7d9f3f843f83a5026eda96c..fc42fe5c07fedbc94ed9c513e80209932adaabe1 100644
--- a/actionpack/lib/action_controller/metal/mime_responds.rb
+++ b/actionpack/lib/action_controller/metal/mime_responds.rb
@@ -229,7 +229,7 @@ def initialize(mimes, variant = nil)
         @responses = {}
         @variant = variant
 
-        mimes.each { |mime| @responses[Mime::Type[mime.to_sym.upcase]] = nil }
+        mimes.each { |mime| @responses[Mime::Type[mime.upcase.to_sym]] = nil }
       end
 
       def any(*args, &block)