diff --git a/xos/models/models.py b/xos/models/models.py
index 6d9b60d..51d379f 100644
--- a/xos/models/models.py
+++ b/xos/models/models.py
@@ -32,4 +32,8 @@
         except self.DoesNotExist:
             pass
 
+        if self.is_new and not self.created_by:
+            # NOTE if created_by is null it has been created by XOS
+            self.created_by = "XOS"
+
         super(MCordSubscriberInstance, self).save(*args, **kwargs)