diff --git a/atreal_openads/models.py b/atreal_openads/models.py
index 81dfcee..5ca4b30 100644
--- a/atreal_openads/models.py
+++ b/atreal_openads/models.py
@@ -36,6 +36,7 @@ from django.utils.translation import ugettext_lazy as _
 from django.core.files.base import ContentFile
 from django.core.exceptions import ValidationError
 from django.utils.encoding import force_text
+from django.utils import six
 
 from passerelle.base.models import BaseResource, HTTPResource
 from passerelle.utils.api import endpoint
@@ -65,6 +66,7 @@ from .utils import (
 )
 
 
+@six.python_2_unicode_compatible
 class ForwardFile(models.Model, BaseModel):  # pylint: disable=too-many-instance-attributes
     """Represent a file uploaded by a user, to be forwarded to openADS.API."""
 
@@ -133,7 +135,7 @@ class ForwardFile(models.Model, BaseModel):  # pylint: disable=too-many-instance
                     self.numero_demande, self.numero_dossier,
                     self.type_fichier, self.orig_filename, self.upload_status)
 
-    def __unicode__(self):
+    def __str__(self):
         return u"%s[%s]" % (trunc_str_values(self.orig_filename, 20), self.get_status())
 
     def get_url_params(self, primary_key=True):
@@ -200,6 +202,7 @@ class ForwardFile(models.Model, BaseModel):  # pylint: disable=too-many-instance
         return ret
 
 
+@six.python_2_unicode_compatible
 class Collectivite(models.Model, BaseModel):
     """Represent a "collectivite"."""
 
@@ -245,11 +248,10 @@ class Collectivite(models.Model, BaseModel):
             force_text(self.connecteur) if hasattr(self, 'connecteur') else None,
             self.openADS_id,
             # pylint: disable=no-member
-            unicode(self.guichet) if hasattr(self, 'guichet') else None)
-
-    def __unicode__(self):
-        return self.name if isinstance(self.name, unicode) else unicode(self.name)
+            force_text(self.guichet) if hasattr(self, 'guichet') else None)
 
+    def __str__(self):
+        return self.name if isinstance(self.name, six.text_type) else force_text(self.name)
     def get_fields_kv(self):
         fields = super(Collectivite, self).get_fields_kv()
         # moving related fields field at the end of the list
@@ -270,6 +272,7 @@ class Collectivite(models.Model, BaseModel):
         return params
 
 
+@six.python_2_unicode_compatible
 class Guichet(models.Model, BaseModel):
     """Represent a "Guichet"."""
 
@@ -315,7 +318,7 @@ class Guichet(models.Model, BaseModel):
             force_text(self.collectivite) if hasattr(self, 'collectivite') else None,
             force_text(self))
 
-    def __unicode__(self):
+    def __str__(self):
         return u'%s %s -> %s %s [%s/%s]' % (
             force_text(self.DAYS[self.ouverture_sem_d - 1][1]),
             # pylint: disable=no-member
@@ -366,6 +369,7 @@ class Guichet(models.Model, BaseModel):
         return False
 
 
+@six.python_2_unicode_compatible
 class AtrealOpenads(BaseResource, HTTPResource, BaseModel):
     """API that proxy/relay communications with/to openADS."""
 
@@ -403,8 +407,8 @@ class AtrealOpenads(BaseResource, HTTPResource, BaseModel):
             self.collectivites.count(),  # pylint: disable=no-member
             self.default_collectivite_openADS_id)
 
-    def __unicode__(self):
-        return self.slug if isinstance(self.slug, unicode) else unicode(self.slug)
+    def __str__(self):
+        return self.slug if isinstance(self.slug, six.string_types) else force_text(self.slug)
 
     def get_url_name(self, prefix='', plural=False):
         return '%s%s' % (prefix + '-' if prefix else '', 'connector')
diff --git a/atreal_openads/utils.py b/atreal_openads/utils.py
index 19fe0de..e1bc79d 100644
--- a/atreal_openads/utils.py
+++ b/atreal_openads/utils.py
@@ -32,6 +32,7 @@ import sys
 from HTMLParser import HTMLParser
 
 from django.urls import reverse_lazy
+from django.utils import six
 from django.utils.encoding import force_text
 
 
@@ -161,6 +162,7 @@ def trunc_str_values(value, limit, visited=None, truncate_text=u'…'):
     return value
 
 
+@six.python_2_unicode_compatible
 class DictDumper(object):
     """Helper to dump a dictionary to a string representation with lazy processing.
 
@@ -184,14 +186,10 @@ class DictDumper(object):
         return u'DictDumper(dic=%r,max_str_len=%r,use_json_dumps=%r)' % (
             self.dic, self.max_str_len, self.use_json_dumps)
 
-    @force_encoded_string_output
     def __str__(self):
-        return unicode(self)
-
-    def __unicode__(self):
         dict_trunc = trunc_str_values(copy.deepcopy(self.dic), self.max_str_len)
         dict_ref = json.dumps(dict_trunc) if self.use_json_dumps else dict_trunc
-        return unicode(dict_ref)
+        return force_text(dict_ref)
 
 
 class BaseModel(object):