diff --git a/acme/acme/client_test.py b/acme/acme/client_test.py
index c8e95a423..7403cde81 100644
--- a/acme/acme/client_test.py
+++ b/acme/acme/client_test.py
@@ -484,9 +484,11 @@ class ClientNetworkTest(unittest.TestCase):
     def test_check_response_not_ok_jobj_no_error(self):
         self.response.ok = False
         self.response.json.return_value = {}
-        # pylint: disable=protected-access
-        self.assertRaises(
-            errors.ClientError, self.net._check_response, self.response)
+        with mock.patch('acme.client.messages.Error.from_json') as from_json:
+            from_json.side_effect = jose.DeserializationError
+            # pylint: disable=protected-access
+            self.assertRaises(
+                errors.ClientError, self.net._check_response, self.response)
 
     def test_check_response_not_ok_jobj_error(self):
         self.response.ok = False
diff --git a/acme/acme/messages.py b/acme/acme/messages.py
index 24a3b580c..40ddbdb2f 100644
--- a/acme/acme/messages.py
+++ b/acme/acme/messages.py
@@ -37,9 +37,9 @@ class Error(jose.JSONObjectWithFields, errors.Error):
         )
     )
 
-    typ = jose.Field('type')
+    typ = jose.Field('type', omitempty=True, default='about:blank')
     title = jose.Field('title', omitempty=True)
-    detail = jose.Field('detail')
+    detail = jose.Field('detail', omitempty=True)
 
     @property
     def description(self):
diff --git a/acme/acme/messages_test.py b/acme/acme/messages_test.py
index b2b7febdc..c1f027302 100644
--- a/acme/acme/messages_test.py
+++ b/acme/acme/messages_test.py
@@ -28,6 +28,14 @@ class ErrorTest(unittest.TestCase):
         self.error_custom = Error(typ='custom', detail='bar')
         self.jobj_cusom = {'type': 'custom', 'detail': 'bar'}
 
+    def test_default_typ(self):
+        from acme.messages import Error
+        self.assertEqual(Error().typ, 'about:blank')
+
+    def test_from_json_empty(self):
+        from acme.messages import Error
+        self.assertEqual(Error(), Error.from_json('{}'))
+
     def test_from_json_hashable(self):
         from acme.messages import Error
         hash(Error.from_json(self.error.to_json()))