diff --git a/pymods/irods_utils/irods_utils.py b/pymods/irods_utils/irods_utils.py
index eb581a736c48ceb83991d5daf5c1b7207efc2d07..da178618bbc5b8342bfaa28cfe5fde7b714f0fab 100644
--- a/pymods/irods_utils/irods_utils.py
+++ b/pymods/irods_utils/irods_utils.py
@@ -597,7 +597,7 @@ def RegisterNewExperiment( exp_form_owner,
 
         # It's a real question whether we need to do this level of userid verification - is it just to keep the riffraff out?
         irods_owner_user, error_message = get_irods_user(irods_sesh, exp_form_owner)
-        if irods_owner_user == None:
+        if irods_owner_user == None and not accept_undefined_user:
             message = "Experiment owner " + exp_form_owner + " is not a registered MrData userid."
             logger.info( message )
             return None, message