diff --git a/Library/Homebrew/extend/os/mac/keg.rb b/Library/Homebrew/extend/os/mac/keg.rb
index c0b1e3fcc3..b2b94d36ff 100644
--- a/Library/Homebrew/extend/os/mac/keg.rb
+++ b/Library/Homebrew/extend/os/mac/keg.rb
@@ -3,4 +3,6 @@
 class Keg
   GENERIC_KEG_LINK_DIRECTORIES = (remove_const :KEG_LINK_DIRECTORIES).freeze
   KEG_LINK_DIRECTORIES = (GENERIC_KEG_LINK_DIRECTORIES + ["Frameworks"]).freeze
+  GENERIC_MUST_EXIST_DIRECTORIES = (remove_const :MUST_EXIST_DIRECTORIES).freeze
+  MUST_EXIST_DIRECTORIES = (GENERIC_MUST_EXIST_DIRECTORIES + [HOMEBREW_PREFIX/"Frameworks"]).uniq.sort.freeze
 end