diff --git a/.travis.yml b/.travis.yml
index e33243d..bce14d9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,10 @@
 language: python
 python:
   - "2.7"
+  - "3.4"
+  - "3.5"
+  - "3.6"
+  - "nightly"
 install:
   - pip install pipenv pew
   - pipenv install --dev --ignore-pipfile
diff --git a/json2cmake/__init__.py b/json2cmake/__init__.py
index 9a503f7..7668a7a 100755
--- a/json2cmake/__init__.py
+++ b/json2cmake/__init__.py
@@ -5,10 +5,15 @@
 import shlex
 import uuid
 
+try:
+    basestring
+except NameError:
+    basestring = str
+
 
 def freeze(obj):
     if isinstance(obj, dict):
-        return freeze(set([freeze(x) for x in obj.iteritems()]))
+        return freeze(set([freeze(x) for x in obj.items()]))
     if isinstance(obj, list):
         return tuple([freeze(x) for x in obj])
     if isinstance(obj, set):
@@ -90,7 +95,7 @@ def write(self, output, directory=None):
         output.write('cmake_minimum_required(VERSION 2.8.8)\n')
         output.write('project(autogenerated)\n\n')
 
-        for (config, files) in self.targets.iteritems():
+        for (config, files) in self.targets.items():
             config = {k: v for (k, v) in config}
             name = uuid.uuid4()