diff --git a/certbot_haproxy/installer.py b/certbot_haproxy/installer.py
index 47eb149..28c5fa4 100644
--- a/certbot_haproxy/installer.py
+++ b/certbot_haproxy/installer.py
@@ -26,6 +26,8 @@
     Be sure to replace `$USER` with the user that will be running the lehaproxy
     installer.
 """
+from builtins import str
+from past.builtins import basestring
 import logging
 import os
 import glob
@@ -134,7 +136,7 @@ class HAProxyInstaller(common.Plugin):
                 " returns letsencrypt certificates. Defaults to the value"
                 " 'h2ppy h2cker fake CA' that is used by the local boulder."
             ),
-            type=unicode,
+            type=str,
             default=u'Let\'s Encrypt Authority X3'
         )
         add(
@@ -464,7 +466,7 @@ class HAProxyInstaller(common.Plugin):
 
         # Write all new files and changes:
         for filepath, contents in \
-                self.new_crt_files.items() + self.crt_files.items():
+                list(self.new_crt_files.items()) + list(self.crt_files.items()):
 
             # Make sure directory of filepath exists
             path = os.path.dirname(os.path.abspath(filepath))
diff --git a/certbot_haproxy/tests/test_installer.py b/certbot_haproxy/tests/test_installer.py
index 7a849c4..b609686 100644
--- a/certbot_haproxy/tests/test_installer.py
+++ b/certbot_haproxy/tests/test_installer.py
@@ -1,4 +1,5 @@
 """Test installer functions"""
+from past.builtins import basestring
 import unittest
 import mock
 import os
@@ -75,7 +76,7 @@ class TestInstaller(unittest.TestCase):
         from OpenSSL import crypto
         self.installer.new_crt_files = {}
         self.installer._fall_back_cert()
-        key = self.installer.new_crt_files.keys()[0]
+        key = list(self.installer.new_crt_files.keys())[0]
         cert = self.installer.new_crt_files[key]
         self.assertIsInstance(key, str)
         self.assertIsInstance(cert, str)
diff --git a/certbot_haproxy/util.py b/certbot_haproxy/util.py
index a55483c..2d388ed 100644
--- a/certbot_haproxy/util.py
+++ b/certbot_haproxy/util.py
@@ -1,6 +1,7 @@
 """
     Utility functions.
 """
+from builtins import object
 
 from OpenSSL import crypto
 import socket