diff --git a/Library/Homebrew/dev-cmd/test-bot.rb b/Library/Homebrew/dev-cmd/test-bot.rb
index f55821e88fca6e254138fb3864aae81522c50d9c..986e1fd4113939747067f3c32cd31f30630f893c 100644
--- a/Library/Homebrew/dev-cmd/test-bot.rb
+++ b/Library/Homebrew/dev-cmd/test-bot.rb
@@ -909,7 +909,6 @@ module Homebrew
 
     ENV["HOMEBREW_DEVELOPER"] = "1"
     ENV["HOMEBREW_SANDBOX"] = "1"
-    ENV["HOMEBREW_RUBY_MACHO"] = "1"
     ENV["HOMEBREW_NO_EMOJI"] = "1"
     ENV["HOMEBREW_FAIL_LOG_LINES"] = "150"
     ENV["HOMEBREW_EXPERIMENTAL_FILTER_FLAGS_ON_DEPS"] = "1"
diff --git a/Library/Homebrew/os/mac/keg.rb b/Library/Homebrew/os/mac/keg.rb
index dcda0908b7856bac4efa2a24305a4e05d9d730d3..201c57b50f6d374b8737769af41287fccc337c9d 100644
--- a/Library/Homebrew/os/mac/keg.rb
+++ b/Library/Homebrew/os/mac/keg.rb
@@ -1,5 +1,5 @@
 class Keg
-  if ENV["HOMEBREW_RUBY_MACHO"]
+  if !ENV["HOMEBREW_NO_RUBY_MACHO"]
     require "os/mac/ruby_keg"
     include RubyKeg
   else
diff --git a/Library/Homebrew/os/mac/pathname.rb b/Library/Homebrew/os/mac/pathname.rb
index 87fc729365bb06054b5340d9f730ada82d0a3ec0..b76c4333a1daa0df904548349bbae6b658113e92 100644
--- a/Library/Homebrew/os/mac/pathname.rb
+++ b/Library/Homebrew/os/mac/pathname.rb
@@ -1,7 +1,7 @@
 require "os/mac/shared_mach"
 
 class Pathname
-  if ENV["HOMEBREW_RUBY_MACHO"]
+  if !ENV["HOMEBREW_NO_RUBY_MACHO"]
     require "os/mac/ruby_mach"
     include RubyMachO
   else