diff --git a/acme/messages2.py b/acme/messages2.py
index ac26d2e97..3db14aa2e 100644
--- a/acme/messages2.py
+++ b/acme/messages2.py
@@ -18,8 +18,8 @@ class Error(jose.JSONObjectWithFields, Exception):
         'badCSR': 'The CSR is unacceptable (e.g., due to a short key)',
     }
 
-    typ = jose.Field('type', omitempty=True)
-    title = jose.Field('title', omitempty=True)
+    typ = jose.Field('type')
+    title = jose.Field('title')
     detail = jose.Field('detail')
 
     @typ.encoder
diff --git a/acme/messages2_test.py b/acme/messages2_test.py
index 5f9441b4f..d10d57973 100644
--- a/acme/messages2_test.py
+++ b/acme/messages2_test.py
@@ -21,7 +21,7 @@ class ErrorTest(unittest.TestCase):
 
     def setUp(self):
         from acme.messages2 import Error
-        self.error = Error(detail='foo', typ='malformed')
+        self.error = Error(detail='foo', typ='malformed', title='title')
 
     def test_typ_prefix(self):
         self.assertEqual('malformed', self.error.typ)
diff --git a/letsencrypt/tests/network2_test.py b/letsencrypt/tests/network2_test.py
index bfe3e89b4..3df5b6dab 100644
--- a/letsencrypt/tests/network2_test.py
+++ b/letsencrypt/tests/network2_test.py
@@ -114,7 +114,8 @@ class NetworkTest(unittest.TestCase):
 
     def test_check_response_not_ok_jobj_error(self):
         self.response.ok = False
-        self.response.json.return_value = messages2.Error(detail='foo')
+        self.response.json.return_value = messages2.Error(
+            detail='foo', typ='serverInternal', title='some title').to_json()
         # pylint: disable=protected-access
         self.assertRaises(
             messages2.Error, self.net._check_response, self.response)