1 files changed, 11 insertions, 0 deletions
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index 8675d8bc1e..e3a4a70e93 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -86,6 +86,13 @@ module Rails
       end
     end
 
+    def config_when_updating
+      foo = File.exist?('config/initializers/cookies_serializer.rb')
+      config
+
+      gsub_file 'config/initializers/cookies_serializer.rb', /json/, 'marshal' unless foo
+    end
+
     def database_yml
       template "config/databases/#{options[:database]}.yml", "config/database.yml"
     end
@@ -188,6 +195,10 @@ module Rails
         build(:config)
       end
 
+      def update_config_files
+        build(:config_when_updating)
+      end
+
       def create_boot_file
         template "config/boot.rb"
       end