diff --git a/Library/Homebrew/cask/denylist.rb b/Library/Homebrew/cask/denylist.rb
index 86bd1151ae..dda4326ba6 100644
--- a/Library/Homebrew/cask/denylist.rb
+++ b/Library/Homebrew/cask/denylist.rb
@@ -1,6 +1,9 @@
 # frozen_string_literal: true
 
 module Cask
+  # List of casks which are not allowed in official taps.
+  #
+  # @api private
   module Denylist
     def self.reason(name)
       case name