diff --git a/actionpack/lib/abstract_controller/base.rb b/actionpack/lib/abstract_controller/base.rb
index 8d1c228657682d14b0ef0255b370885821bd1d48..c00f0d0c6f221425d9a80fd95528a8d82cf3e929 100644
--- a/actionpack/lib/abstract_controller/base.rb
+++ b/actionpack/lib/abstract_controller/base.rb
@@ -8,7 +8,8 @@ module AbstractController
   class Error < StandardError #:nodoc:
   end
 
-  class ActionNotFound < StandardError #:nodoc:
+  # Raised when a non-existing controller action is triggered.
+  class ActionNotFound < StandardError
   end
 
   # <tt>AbstractController::Base</tt> is a low-level API. Nobody should be