diff --git a/Library/Homebrew/cask/utils.rb b/Library/Homebrew/cask/utils.rb
index a4b521bc2e..8cee597600 100644
--- a/Library/Homebrew/cask/utils.rb
+++ b/Library/Homebrew/cask/utils.rb
@@ -8,6 +8,9 @@ require "stringio"
 BUG_REPORTS_URL = "https://github.com/Homebrew/homebrew-cask#reporting-bugs"
 
 module Cask
+  # Helper functions for various cask operations.
+  #
+  # @api private
   module Utils
     def self.gain_permissions_remove(path, command: SystemCommand)
       if path.respond_to?(:rmtree) && path.exist?