diff --git a/acme/acme/messages.py b/acme/acme/messages.py
index 0b73864ec..3b5739da1 100644
--- a/acme/acme/messages.py
+++ b/acme/acme/messages.py
@@ -25,6 +25,8 @@ class Error(jose.JSONObjectWithFields, errors.Error):
             ('connection', 'The server could not connect to the client to '
                 'verify the domain'),
             ('dnssec', 'The server could not validate a DNSSEC signed domain'),
+            ('invalidEmail',
+             'The provided email for a registration was invalid'),
             ('malformed', 'The request message was malformed'),
             ('rateLimited', 'There were too many requests of a given type'),
             ('serverInternal', 'The server experienced an internal error'),