diff --git a/lib/valid_attribute.rb b/lib/valid_attribute.rb
index 24e2d7d..f4e7da1 100644
--- a/lib/valid_attribute.rb
+++ b/lib/valid_attribute.rb
@@ -11,6 +11,6 @@ class NoValues < StandardError; end
   require 'valid_attribute/spec'
 elsif defined?(MiniTest::Matchers)
   require 'valid_attribute/minitest'
-else
+elsif defined?(Test::Unit)
   require 'valid_attribute/test_unit'
 end