diff --git a/acme/acme/client.py b/acme/acme/client.py
index 79bfa0871..26ee6e6ad 100644
--- a/acme/acme/client.py
+++ b/acme/acme/client.py
@@ -49,6 +49,7 @@ class Client(object):  # pylint: disable=too-many-instance-attributes
     :ivar messages.Directory directory:
     :ivar key: `.JWK` (private)
     :ivar account: `.Account` (private)
+    :ivar acme_version: `int` (private) 1 for ACMEv1, or 2 for ACMEv2.
     :ivar alg: `.JWASignature`
     :ivar bool verify_ssl: Verify SSL certificates?
     :ivar .ClientNetwork net: Client network. Useful for testing. If not
@@ -57,8 +58,8 @@ class Client(object):  # pylint: disable=too-many-instance-attributes
 
     """
 
-    def __init__(self, directory, key, account=None, alg=jose.RS256, verify_ssl=True,
-                 net=None):
+    def __init__(self, directory, key, account=None, acme_version=1, alg=jose.RS256,
+                 verify_ssl=True, net=None):
         """Initialize.
 
         :param directory: Directory Resource (`.messages.Directory`) or
@@ -67,8 +68,9 @@ class Client(object):  # pylint: disable=too-many-instance-attributes
         """
         self.key = key
         self.account = account
-        self.net = ClientNetwork(key, account=account, alg=alg,
-            verify_ssl=verify_ssl) if net is None else net
+        self.acme_version = acme_version
+        self.net = ClientNetwork(key, account=account, acme_version=acme_version,
+            alg=alg, verify_ssl=verify_ssl) if net is None else net
 
         if isinstance(directory, six.string_types):
             self.directory = messages.Directory.from_json(
@@ -574,9 +576,9 @@ class ClientNetwork(object):  # pylint: disable=too-many-instance-attributes
     JSON_ERROR_CONTENT_TYPE = 'application/problem+json'
     REPLAY_NONCE_HEADER = 'Replay-Nonce'
 
-    def __init__(self, key, account=None, alg=jose.RS256, verify_ssl=True,
-                 user_agent='acme-python', timeout=DEFAULT_NETWORK_TIMEOUT,
-                 acme_version=2):
+    def __init__(self, key, account=None, acme_version=1, alg=jose.RS256,
+                 verify_ssl=True, user_agent='acme-python',
+                 timeout=DEFAULT_NETWORK_TIMEOUT):
         self.key = key
         self.account = account
         self.alg = alg
diff --git a/chisel2.py b/chisel2.py
index 49f13b3a8..3c7d91193 100644
--- a/chisel2.py
+++ b/chisel2.py
@@ -42,10 +42,10 @@ def make_client(email=None):
     """Build an acme.Client and register a new account with a random key."""
     key = jose.JWKRSA(key=rsa.generate_private_key(65537, 2048, default_backend()))
 
-    net = acme_client.ClientNetwork(key, verify_ssl=False,
+    net = acme_client.ClientNetwork(key, verify_ssl=False, acme_version=2,
                                     user_agent="Boulder integration tester")
 
-    client = acme_client.Client(DIRECTORY, key=key, net=net)
+    client = acme_client.Client(DIRECTORY, key=key, net=net, acme_version=2)
     tos = client.directory.meta.terms_of_service
     if tos is not None and "Do%20what%20thou%20wilt" in tos:
         net.account = client.register(messages.NewRegistration.from_data(email=email,