diff --git a/actionpack/actionpack.gemspec b/actionpack/actionpack.gemspec
index 8a7169bfa1..00c4d7de1c 100644
--- a/actionpack/actionpack.gemspec
+++ b/actionpack/actionpack.gemspec
@@ -21,6 +21,6 @@ Gem::Specification.new do |s|
   s.add_dependency('activemodel',   '= 3.0.0.beta1')
   s.add_dependency('rack',          '~> 1.1.0')
   s.add_dependency('rack-test',     '~> 0.5.0')
-  s.add_dependency('rack-mount',    '~> 0.4.7')
+  s.add_dependency('rack-mount',    '~> 0.5.1')
   s.add_dependency('erubis',        '~> 2.6.5')
 end
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index dcf98b729b..ee60112bbc 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -431,7 +431,7 @@ module ActionDispatch
         end
 
         req = Rack::Request.new(env)
-        @set.recognize(req) do |route, params|
+        @set.recognize(req) do |route, matches, params|
           dispatcher = route.app
           if dispatcher.is_a?(Dispatcher) && dispatcher.controller(params)
             dispatcher.prepare_params!(params)