diff --git a/virtualenv/pfidp/auth_backend.py b/virtualenv/pfidp/auth_backend.py
index 349b808..fd521b3 100644
--- a/virtualenv/pfidp/auth_backend.py
+++ b/virtualenv/pfidp/auth_backend.py
@@ -40,6 +40,7 @@ class TransientUser(SAML2TransientUser):
 
     def __init__(self, pfuser, privileges):
         self.id = pfuser['username']
+        self.pk = self.id
         self.displayname = pfuser['displayname'].decode('latin1')
         self.univnautes_privileges = privileges
         if privileges and 'univnautes-idp-admin' in privileges: