diff --git a/test/unit/mailer_test.rb b/test/unit/mailer_test.rb
index 5024a845..d58d5590 100644
--- a/test/unit/mailer_test.rb
+++ b/test/unit/mailer_test.rb
@@ -133,7 +133,7 @@ class MailerTest < ActiveSupport::TestCase
     mail = ActionMailer::Base.deliveries.last
     assert_not_nil mail
     assert_equal Mailer.message_id_for(journal), mail.message_id
-    assert_equal Mailer.message_id_for(journal.issue), mail.references.to_s
+    assert_equal Mailer.message_id_for(journal.issue), mail.references.first.to_s
   end
   
   def test_message_posted_message_id
@@ -153,7 +153,7 @@ class MailerTest < ActiveSupport::TestCase
     mail = ActionMailer::Base.deliveries.last
     assert_not_nil mail
     assert_equal Mailer.message_id_for(message), mail.message_id
-    assert_equal Mailer.message_id_for(message.parent), mail.references.to_s
+    assert_equal Mailer.message_id_for(message.parent), mail.references.first.to_s
   end
   
   # test mailer methods for each language