diff --git a/actionpack/lib/action_dispatch/testing/assertions/routing.rb b/actionpack/lib/action_dispatch/testing/assertions/routing.rb
index 1499c03bdf..9338fa9e70 100644
--- a/actionpack/lib/action_dispatch/testing/assertions/routing.rb
+++ b/actionpack/lib/action_dispatch/testing/assertions/routing.rb
@@ -53,7 +53,6 @@ def assert_recognizes(expected_options, path, extras={}, message=nil)
         extras.each_key { |key| expected_options.delete key } unless extras.nil?
 
         expected_options.stringify_keys!
-        routing_diff = expected_options.diff(request.path_parameters)
         msg = build_message(message, "The recognized options <?> did not match <?>, difference: <?>",
             request.path_parameters, expected_options, expected_options.diff(request.path_parameters))
         assert_block(msg) { request.path_parameters == expected_options }