diff --git a/passbook/providers/saml/processors/assertion.py b/passbook/providers/saml/processors/assertion.py
index 014817a88..d5e5fdab9 100644
--- a/passbook/providers/saml/processors/assertion.py
+++ b/passbook/providers/saml/processors/assertion.py
@@ -173,7 +173,7 @@ class AssertionProcessor:
         )
         if self.auth_n_request.id:
             subject_confirmation_data.attrib["InResponseTo"] = self.auth_n_request.id
-        subject_confirmation_data.attrib["NotOnOrAfter"] = self._issue_instant
+        subject_confirmation_data.attrib["NotOnOrAfter"] = self._valid_not_on_or_after
         subject_confirmation_data.attrib["Recipient"] = self.provider.acs_url
         return subject