diff --git a/modoboa/admin/models/domain.py b/modoboa/admin/models/domain.py
index 50a04d97b..6d942d5e6 100644
--- a/modoboa/admin/models/domain.py
+++ b/modoboa/admin/models/domain.py
@@ -334,6 +334,9 @@ class MXRecord(models.Model):
     def __unicode__(self):
         return u"{0.name} ({0.address}) for {0.domain} ".format(self)
 
+    def __str__(self):
+        return "{0.name} ({0.address}) for {0.domain} ".format(self)
+
 
 class DNSBLQuerySet(models.QuerySet):
     """Custom manager for DNSBLResultManager."""
diff --git a/modoboa/core/models.py b/modoboa/core/models.py
index 3bdaa7a22..376e43697 100644
--- a/modoboa/core/models.py
+++ b/modoboa/core/models.py
@@ -420,6 +420,11 @@ class ObjectAccess(models.Model):
             self.user, self.content_object, self.content_type
         )
 
+    def __str__(self):
+        return "%s => %s (%s)" % (
+            self.user, self.content_object, self.content_type
+        )
+
 
 class Log(models.Model):
     """Simple log in database."""
diff --git a/modoboa/lib/form_utils.py b/modoboa/lib/form_utils.py
index e2b7144b1..cbea6ad4b 100644
--- a/modoboa/lib/form_utils.py
+++ b/modoboa/lib/form_utils.py
@@ -384,6 +384,17 @@ class CustomRadioInput(RadioChoiceInput):
             % (label_for, self.tag(), choice_label)
         )
 
+    def __str__(self):
+        if "id" in self.attrs:
+            label_for = ' for="%s"' % self.attrs["id"]
+        else:
+            label_for = ""
+        choice_label = conditional_escape(force_text(self.choice_label))
+        return mark_safe(
+            "<label class='radio-inline' %s>%s %s</label>"
+            % (label_for, self.tag(), choice_label)
+        )
+
 
 class InlineRadioRenderer(RadioSelect.renderer):
     """Custom inline radio renderer."""