diff --git a/combo_plugin_gnm/templatetags/gnm.py b/combo_plugin_gnm/templatetags/gnm.py
index d462009..b2df54f 100644
--- a/combo_plugin_gnm/templatetags/gnm.py
+++ b/combo_plugin_gnm/templatetags/gnm.py
@@ -31,6 +31,7 @@ from django import template
 from django.conf import settings
 from django.core.serializers.json import DjangoJSONEncoder
 from django.core import signing
+from django.utils import six
 from django.utils.dateparse import parse_datetime
 from django.utils.http import quote
 from django.utils.html import format_html
@@ -476,7 +477,7 @@ def as_commune(user_data):
     if not user_data:
         return None
 
-    if isinstance(user_data, basestring):
+    if isinstance(user_data, six.string_types):
         # user_data is expected to be (page) slug
         collectivities = get_gnm_collectivities()
         for collectivity in collectivities: