diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 78c31c527e..e4d2ecaba1 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -47,7 +47,7 @@ Let's say you have a controller called `ProductsController` and an `index` actio
 
 By default, the page cache directory is set to `Rails.public_path` (which is usually set to the `public` folder) and this can be configured by changing the configuration setting `config.action_controller.page_cache_directory`. Changing the default from `public` helps avoid naming conflicts, since you may want to put other static html in `public`, but changing this will require web server reconfiguration to let the web server know where to serve the cached files from.
 
-The Page Caching mechanism will automatically add a `.html` extension to requests for pages that do not have an extension to make it easy for the webserver to find those pages and this can be configured by changing the configuration setting `config.action_controller.page_cache_extension`.
+The Page Caching mechanism will automatically add a `.html` extension to requests for pages that do not have an extension to make it easy for the webserver to find those pages and this can be configured by changing the configuration setting `config.action_controller.default_static_extension`.
 
 In order to expire this page when a new product is added we could extend our example controller like this: