diff --git a/compressor/tests/test_signals.py b/compressor/tests/test_signals.py
index b4ece9c..107b121 100644
--- a/compressor/tests/test_signals.py
+++ b/compressor/tests/test_signals.py
@@ -34,9 +34,9 @@ class PostCompressSignalTestCase(TestCase):
         post_compress.connect(callback)
         self.js_node.output()
         args, kwargs = callback.call_args
-        self.assertEquals(JsCompressor, kwargs['sender'])
-        self.assertEquals('js', kwargs['type'])
-        self.assertEquals('file', kwargs['mode'])
+        self.assertEqual(JsCompressor, kwargs['sender'])
+        self.assertEqual('js', kwargs['type'])
+        self.assertEqual('file', kwargs['mode'])
         context = kwargs['context']
         assert 'url' in context['compressed']
 
@@ -47,9 +47,9 @@ class PostCompressSignalTestCase(TestCase):
         post_compress.connect(callback)
         self.css_node.output()
         args, kwargs = callback.call_args
-        self.assertEquals(CssCompressor, kwargs['sender'])
-        self.assertEquals('css', kwargs['type'])
-        self.assertEquals('file', kwargs['mode'])
+        self.assertEqual(CssCompressor, kwargs['sender'])
+        self.assertEqual('css', kwargs['type'])
+        self.assertEqual('file', kwargs['mode'])
         context = kwargs['context']
         assert 'url' in context['compressed']
 
@@ -65,4 +65,4 @@ class PostCompressSignalTestCase(TestCase):
         callback = Mock(wraps=listener)
         post_compress.connect(callback)
         css_node.output()
-        self.assertEquals(3, callback.call_count)
+        self.assertEqual(3, callback.call_count)
diff --git a/compressor/utils/stringformat.py b/compressor/utils/stringformat.py
index 3be63e4..0fd3f6d 100644
--- a/compressor/utils/stringformat.py
+++ b/compressor/utils/stringformat.py
@@ -8,6 +8,8 @@ Author: Florent Xicluna
 
 import re
 
+from django.utils import six
+
 _format_str_re = re.compile(
     r'((?<!{)(?:{{)+'                       # '{{'
     r'|(?:}})+(?!})'                        # '}}
@@ -128,7 +130,7 @@ def _format_field(value, parts, conv, spec, want_bytes=False):
         value = value.strftime(str(spec))
     else:
         value = _strformat(value, spec)
-    if want_bytes and isinstance(value, unicode):
+    if want_bytes and isinstance(value, six.text_type):
         return str(value)
     return value
 
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..c10391c
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,97 @@
+[tox]
+distribute = False
+envlist =
+    py33-1.5.X,
+    py32-1.5.X,
+    py27-1.5.X,
+    py26-1.5.X,
+    py27-1.4.X,
+    py26-1.4.X
+
+[testenv]
+downloadcache = {toxworkdir}/_download/
+commands =
+    django-admin.py --version
+    make test
+
+[testenv:py33-1.5.X]
+basepython = python3.3
+deps =
+    Django>=1.5,<1.6
+    flake8
+    django-discover-runner
+    coverage
+    html5lib
+    mock
+    jinja2
+    lxml
+    BeautifulSoup4
+
+[testenv:py32-1.5.X]
+basepython = python3.2
+deps =
+    Django>=1.5,<1.6
+    flake8
+    django-discover-runner
+    coverage
+    html5lib
+    mock
+    jinja2
+    lxml
+    BeautifulSoup4
+
+[testenv:py27-1.5.X]
+basepython = python2.7
+deps =
+    Django>=1.5,<1.6
+    flake8
+    django-discover-runner
+    coverage
+    html5lib
+    mock
+    jinja2
+    lxml
+    BeautifulSoup
+    unittest2
+
+[testenv:py26-1.5.X]
+basepython = python2.6
+deps =
+    Django>=1.5,<1.6
+    flake8
+    django-discover-runner
+    coverage
+    html5lib
+    mock
+    jinja2
+    lxml
+    BeautifulSoup
+    unittest2
+
+[testenv:py27-1.4.X]
+basepython = python2.7
+deps =
+    Django>=1.4,<1.5
+    flake8
+    django-discover-runner
+    coverage
+    html5lib
+    mock
+    jinja2
+    lxml
+    BeautifulSoup
+    unittest2
+
+[testenv:py26-1.4.X]
+basepython = python2.6
+deps =
+    Django>=1.4,<1.5
+    flake8
+    django-discover-runner
+    coverage
+    html5lib
+    mock
+    jinja2
+    lxml
+    BeautifulSoup
+    unittest2