diff --git a/oidc_provider/models.py b/oidc_provider/models.py
index f49689c..6504238 100644
--- a/oidc_provider/models.py
+++ b/oidc_provider/models.py
@@ -30,7 +30,14 @@ JWT_ALGS = [
 ]
 
 
+class ResponseTypeManager(models.Manager):
+    def get_by_natural_key(self, value):
+        return self.get(value=value)
+
+
 class ResponseType(models.Model):
+    objects = ResponseTypeManager()
+
     value = models.CharField(
         max_length=30,
         choices=RESPONSE_TYPE_CHOICES,
@@ -40,6 +47,9 @@ class ResponseType(models.Model):
         max_length=50,
     )
 
+    def natural_key(self):
+        return self.value,  # natural_key must return tuple
+
     def __str__(self):
         return u'{0}'.format(self.description)