diff --git a/avatar/models.py b/avatar/models.py
index 1463df0..e7127ff 100644
--- a/avatar/models.py
+++ b/avatar/models.py
@@ -72,6 +72,7 @@ class Avatar(models.Model):
 
     class Meta:
         app_label = 'avatar'
+        unique_together = ('user', 'primary')
 
     def __unicode__(self):
         return _(six.u('Avatar for %s')) % self.user