diff --git a/src/authentic2_idp_oidc/views.py b/src/authentic2_idp_oidc/views.py
index 2518daca3..b3527fd54 100644
--- a/src/authentic2_idp_oidc/views.py
+++ b/src/authentic2_idp_oidc/views.py
@@ -431,7 +431,7 @@ def authorize_for_client(request, client, redirect_uri):
         need_access_token = 'token' in response_type.split()
         if need_access_token:
             if client.access_token_duration is None:
-                expires_in = datetime.timedelta(request.session.get_expiry_age())
+                expires_in = datetime.timedelta(seconds=request.session.get_expiry_age())
                 expired = None
             else:
                 expires_in = client.access_token_duration