diff --git a/examples/restified.py b/examples/restified.py
index 1428c96cc..99d07a067 100644
--- a/examples/restified.py
+++ b/examples/restified.py
@@ -34,4 +34,7 @@ logging.debug(authzr)
 
 csr = M2Crypto.X509.load_request_string(pkg_resources.resource_string(
     'letsencrypt.client.tests', os.path.join('testdata', 'csr.pem')))
-net.request_issuance(csr, (authzr,))
+try:
+    net.request_issuance(csr, (authzr,))
+except messages2.Error as error:
+    print error.detail
diff --git a/letsencrypt/acme/messages2.py b/letsencrypt/acme/messages2.py
index 37a384aa4..903746ae7 100644
--- a/letsencrypt/acme/messages2.py
+++ b/letsencrypt/acme/messages2.py
@@ -8,7 +8,7 @@ from letsencrypt.acme import other
 from letsencrypt.acme import util
 
 
-class Error(jose.JSONObjectWithFields):
+class Error(jose.JSONObjectWithFields, Exception):
     """ACME error.
 
     https://tools.ietf.org/html/draft-ietf-appsawg-http-problem-00
@@ -23,10 +23,11 @@ class Error(jose.JSONObjectWithFields):
         "badCSR": "The CSR is unacceptable (e.g., due to a short key)",
     }
 
-    typ = jose.Field('type')
+    typ = jose.Field('type', omitempty=True)  # Boulder omits, spec requires
     title = jose.Field('title', omitempty=True)
     detail = jose.Field('detail')
-    instance = jose.Field('instance')
+    # Boulder omits, spec requires
+    instance = jose.Field('instance', omitempty=True)
 
     @typ.encoder
     def typ(value):
diff --git a/letsencrypt/client/network2.py b/letsencrypt/client/network2.py
index b2bfb8220..3c68a17c7 100644
--- a/letsencrypt/client/network2.py
+++ b/letsencrypt/client/network2.py
@@ -33,9 +33,16 @@ class Network(object):
             payload=dumps, key=self.key, alg=self.alg).json_dumps()
 
     def _post(self, uri, data):
+        """Send POST data.
+
+        :raises letsencrypt.acme.messages2.Error:
+
+        """
         logging.debug('Sending data: %s', data)
         response = requests.post(uri, data)
         logging.debug('Received response %s: %s', response, response.text)
+        if not response.ok:
+            raise messages2.Error.from_json(response.json())
         return response
 
     def _regr_from_response(self, response, uri=None, new_authz_uri=None):