diff --git a/test/unit/i18n_test.rb b/test/unit/i18n_test.rb
index 2fb13824c..19b9afcfd 100644
--- a/test/unit/i18n_test.rb
+++ b/test/unit/i18n_test.rb
@@ -48,6 +48,8 @@ class I18nTest < ActiveSupport::TestCase
           end
         end
       end
+
+      assert ["ltr", "rtl"].include?(I18n.t("html.dir", :locale => locale)), "html.dir must be ltr or rtl"
     end
   end
 private