https://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/3457-actioncontrollercachingsweeper-controller-instance-is-not-thread-safe I ran in to this error "NoMethodError (undefined method `controller_name'' for nil:NilClass)" when trying to use config.threadsafety!. The patch by the OP works for me. I''m on Rails 2.3.10, but glancing at the code I believe it applies to Rails 3 as well. -Greg -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. To post to this group, send email to rubyonrails-core@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-core+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-core?hl=en.