diff --git a/Library/Homebrew/test/testing_env.rb b/Library/Homebrew/test/testing_env.rb
index a35ad3f496..a975a83e14 100644
--- a/Library/Homebrew/test/testing_env.rb
+++ b/Library/Homebrew/test/testing_env.rb
@@ -88,3 +88,10 @@ module VersionAssertions
     assert_nil Version.parse(url)
   end
 end
+
+module Test::Unit::Assertions
+  def assert_empty(obj, msg=nil)
+    assert_respond_to(obj, :empty?, msg)
+    assert(obj.empty?, msg)
+  end if RUBY_VERSION.to_f <= 1.8
+end