diff --git a/muk_web_preview_mail/tests/test_mail_parse.py b/muk_web_preview_mail/tests/test_mail_parse.py
index 16f73c9..40ff538 100644
--- a/muk_web_preview_mail/tests/test_mail_parse.py
+++ b/muk_web_preview_mail/tests/test_mail_parse.py
@@ -61,4 +61,4 @@ class MailParseTestCase(common.HttpCase):
         query.update(params)
         url_parts[4] = urlencode(query)
         url = urlunparse(url_parts)
-        self.url_open(url)      
\ No newline at end of file
+        self.assertTrue(self.url_open(url))      
\ No newline at end of file