diff --git a/letsencrypt/client/acme.py b/letsencrypt/client/acme.py
index 7aec6e595..52ac1e4bd 100644
--- a/letsencrypt/client/acme.py
+++ b/letsencrypt/client/acme.py
@@ -70,8 +70,7 @@ def challenge_request(name):
     :rtype: dict
 
     """
-
-    if type(name) is not unicode:
+    if not isinstance(name, unicode):
         raise TypeError("Parameter 'name' must be unicode")
 
     if not name:
@@ -97,28 +96,28 @@ def authorization_request(req_id, name, server_nonce, responses, key):
     :rtype: dict
 
     """
-    if type(req_id) is not str:
+    if not isinstance(req_id, str):
         raise TypeError("Parameter 'req_id' must be of type str")
 
     if not req_id:
         raise ValueError("Parameter 'req_id' must not be empty")
 
-    if type(name) is not unicode:
+    if not isinstance(name, unicode):
         raise TypeError("Parameter 'name' must be of type unicode")
 
     if not name:
         raise ValueError("Parameter 'name' must not be empty")
 
-    if type(server_nonce) is not str:
+    if not isinstance(server_nonce, str):
         raise TypeError("Parameter 'server_nonce' must be of type str")
 
     if not server_nonce:
         raise ValueError("Parameter 'server_nonce' must not be empty")
 
-    if type(responses) is not list:
+    if not isinstance(responses, list):
         raise TypeError("Parameter 'responses' must be of type list")
 
-    if type(key) is not str:
+    if not isinstance(key, str):
         raise TypeError("Parameter 'key' must be of type str")
 
     if not key:
@@ -145,13 +144,13 @@ def certificate_request(csr_der, key):
     :rtype: dict
 
     """
-    if type(csr_der) is not str:
+    if not isinstance(csr_der, str):
         raise TypeError("Parameter 'csr_der' must be of type str")
 
     if not csr_der:
         raise ValueError("Parameter 'csr_der' must not be empty")
 
-    if type(key) is not str:
+    if not isinstance(key, str):
         raise TypeError("Parameter 'key' must be of type str")
 
     if not key:
@@ -176,13 +175,13 @@ def revocation_request(key_file, cert_der):
     :rtype: dict
 
     """
-    if type(key_file) is not str:
+    if not isinstance(key_file, str):
         raise TypeError("Parameter 'key_file' must be of type str")
 
     if not key_file:
         raise ValueError("Parameter 'key_file' must not be empty")
 
-    if type(cert_der) is not str:
+    if not isinstance(cert_der, str):
         raise TypeError("Parameter 'cert_der' must be of type str")
 
     if not cert_der:
@@ -204,7 +203,7 @@ def status_request(token):
     :rtype: dict
 
     """
-    if type(token) is not str:
+    if not isinstance(token, str):
         raise TypeError("Parameter 'token' must be of type str")
 
     if not token: