diff --git a/Library/Homebrew/extend/ENV/std.rb b/Library/Homebrew/extend/ENV/std.rb
index dae9959b69..9b150eae01 100644
--- a/Library/Homebrew/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/ENV/std.rb
@@ -1,6 +1,7 @@
 require "hardware"
 require "extend/ENV/shared"
 
+# TODO: deprecate compiling related codes after it's only used by brew test.
 # @private
 module Stdenv
   include SharedEnvExtension