diff --git a/Library/Homebrew/cask/caskroom.rb b/Library/Homebrew/cask/caskroom.rb
index 542ea0bcad..e3519440bb 100644
--- a/Library/Homebrew/cask/caskroom.rb
+++ b/Library/Homebrew/cask/caskroom.rb
@@ -3,6 +3,9 @@
 require "utils/user"
 
 module Cask
+  # Helper functions for interacting with the `Caskroom` directory.
+  #
+  # @api private
   module Caskroom
     module_function