diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index 296ae8ead29d..d2ba23a5fbc7 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -468,7 +468,7 @@ class Comment < ActiveRecord::Base
     test "filter_parameters should be able to set via config.filter_parameters" do
       add_to_config <<-RUBY
         config.filter_parameters += [ :foo, 'bar', lambda { |key, value|
-          value = value.reverse if /baz/.match?(key)
+          value.reverse! if /baz/.match?(key)
         }]
       RUBY