diff --git a/pinax/referrals/models.py b/pinax/referrals/models.py
index <HASH>..<HASH> 100644
--- a/pinax/referrals/models.py
+++ b/pinax/referrals/models.py
@@ -156,8 +156,8 @@ class ReferralResponse(models.Model):
     ip_address = models.CharField(max_length=45)
     action = models.CharField(max_length=128)
 
-    target_content_type = models.ForeignKey(ContentType, null=True, on_delete=models.SET_NULL)
-    target_object_id = models.PositiveIntegerField(null=True)
+    target_content_type = models.ForeignKey(ContentType, null=True, blank=True, on_delete=models.SET_NULL)
+    target_object_id = models.PositiveIntegerField(null=True, blank=True)
     target = GenericForeignKey(
         ct_field="target_content_type",
         fk_field="target_object_id"
don't require context type fields (which are often blank)