diff --git a/passerelle/apps/choosit/models.py b/passerelle/apps/choosit/models.py
index 0bb2cc99..026da911 100644
--- a/passerelle/apps/choosit/models.py
+++ b/passerelle/apps/choosit/models.py
@@ -2,6 +2,7 @@
 import json
 import requests
 
+from django.utils.six import string_types
 from django.utils.translation import ugettext_lazy as _
 from django.db import models
 
@@ -104,7 +105,7 @@ class ChoositSMSGateway(BaseResource, SMSGatewayMixin):
                         results.append(u'Choosit error: %s' % output['error'])
                     else:
                         results.append(output)
-        if any(isinstance(result, basestring) for result in results):
+        if any(isinstance(result, string_types) for result in results):
             raise APIError('Choosit error: some destinations failed',
                            data=list(zip(destinations, results)))
         return list(zip(destinations, results))