diff --git a/certbot-compatibility-test/certbot_compatibility_test/validator.py b/certbot-compatibility-test/certbot_compatibility_test/validator.py
index 1215b1a30..5794633c2 100644
--- a/certbot-compatibility-test/certbot_compatibility_test/validator.py
+++ b/certbot-compatibility-test/certbot_compatibility_test/validator.py
@@ -18,11 +18,11 @@ class Validator(object):
         """Verifies the certificate presented at name is cert"""
         if alt_host is None:
             host = socket.gethostbyname(name).encode()
-        elif isinstance(alt_host, six.binary_type):
+        elif isinstance(alt_host, bytes):
             host = alt_host
         else:
             host = alt_host.encode()
-        name = name if isinstance(name, six.binary_type) else name.encode()
+        name = name if isinstance(name, bytes) else name.encode()
 
         try:
             presented_cert = crypto_util.probe_sni(name, host, port)
diff --git a/certbot/certbot/util.py b/certbot/certbot/util.py
index 8db5ab34a..a87afe079 100644
--- a/certbot/certbot/util.py
+++ b/certbot/certbot/util.py
@@ -517,7 +517,7 @@ def enforce_domain_sanity(domain):
     """
     # Unicode
     try:
-        if isinstance(domain, six.binary_type):
+        if isinstance(domain, bytes):
             domain = domain.decode('utf-8')
         domain.encode('ascii')
     except UnicodeError: