3 files changed, 10 insertions, 3 deletions
diff --git a/actionpack/lib/action_dispatch/http/request.rb b/actionpack/lib/action_dispatch/http/request.rb
index 75be2cc260..c24b404e2f 100755
--- a/actionpack/lib/action_dispatch/http/request.rb
+++ b/actionpack/lib/action_dispatch/http/request.rb
@@ -6,6 +6,7 @@ require 'active_support/memoizable'
 require 'active_support/core_ext/array/wrap'
 require 'active_support/core_ext/hash/indifferent_access'
 require 'active_support/core_ext/object/tap'
+require 'active_support/core_ext/string/access'
 
 module ActionDispatch
   class Request < Rack::Request
@@ -166,7 +167,7 @@ module ActionDispatch
 
       @env["action_dispatch.request.formats"] ||=
         if parameters[:format]
-          [Mime[parameters[:format]]]
+          Array.wrap(Mime[parameters[:format]])
         elsif xhr? || (accept && !accept.include?(?,))
           accepts
         else
diff --git a/actionpack/lib/action_dispatch/middleware/stack.rb b/actionpack/lib/action_dispatch/middleware/stack.rb
index 4f71ea6165..3b27309f58 100644
--- a/actionpack/lib/action_dispatch/middleware/stack.rb
+++ b/actionpack/lib/action_dispatch/middleware/stack.rb
@@ -1,3 +1,5 @@
+require "active_support/inflector/methods"
+
 module ActionDispatch
   class MiddlewareStack < Array
     class Middleware
@@ -32,7 +34,7 @@ module ActionDispatch
         elsif @klass.respond_to?(:call)
           @klass.call
         else
-          @klass.to_s.constantize
+          ActiveSupport::Inflector.constantize(@klass.to_s)
         end
       end
 
@@ -53,7 +55,7 @@ module ActionDispatch
         when Class
           klass == middleware
         else
-          klass == middleware.to_s.constantize
+          klass == ActiveSupport::Inflector.constantize(middleware.to_s)
         end
       end
 
diff --git a/actionpack/test/dispatch/request_test.rb b/actionpack/test/dispatch/request_test.rb
index 239fda98e0..b62df9a6b2 100644
--- a/actionpack/test/dispatch/request_test.rb
+++ b/actionpack/test/dispatch/request_test.rb
@@ -432,6 +432,10 @@ class RequestTest < ActiveSupport::TestCase
     request = stub_request
     request.expects(:parameters).at_least_once.returns({ :format => :txt })
     assert_equal with_set(Mime::TEXT), request.formats
+
+    request = stub_request
+    request.expects(:parameters).at_least_once.returns({ :format => :unknown })
+    assert request.formats.empty?
   end
 
   test "negotiate_mime" do