diff --git a/Library/Homebrew/test/test_bottles.rb b/Library/Homebrew/test/test_bottles.rb
index f443020716..8f5104f36a 100644
--- a/Library/Homebrew/test/test_bottles.rb
+++ b/Library/Homebrew/test/test_bottles.rb
@@ -4,16 +4,18 @@ require 'test/testball'
 # We temporarily redefine bottles_supported? because the
 # following tests assume it is true, but other tests may
 # expect the real value.
-def bottles_are_supported &block
-  alias :old_bottles_supported? :bottles_supported?
-  def bottles_supported?; true end
-  instance_eval(&block)
-  def bottles_supported?; old_bottles_supported? end
+module MacOS extend self
+  def bottles_are_supported
+    alias :old_bottles_supported? :bottles_supported?
+    def bottles_supported?; true end
+    yield
+    def bottles_supported?; old_bottles_supported? end
+  end
 end
 
 class BottleTests < Test::Unit::TestCase
   def test_bottle_spec_selection
-    bottles_are_supported do
+    MacOS.bottles_are_supported do
       f = SnowLeopardBottleSpecTestBall.new
 
       assert_equal case MacOS.cat