diff --git a/configuration/schedulers/foundry.py b/configuration/schedulers/foundry.py
index b8215616f..0ae4f6191 100644
--- a/configuration/schedulers/foundry.py
+++ b/configuration/schedulers/foundry.py
@@ -39,6 +39,7 @@ def _server_source_parameters():
                 ),
                 default="",
                 required=False,
+                regex=r"^([0-9]+)?\Z",
             )
         )
     return parameters