diff --git a/modules/restricted-guests/synapse/synapse_guest_module/guest_registration_servlet.py b/modules/restricted-guests/synapse/synapse_guest_module/guest_registration_servlet.py
index 9835ab7e10..fcf1469161 100644
--- a/modules/restricted-guests/synapse/synapse_guest_module/guest_registration_servlet.py
+++ b/modules/restricted-guests/synapse/synapse_guest_module/guest_registration_servlet.py
@@ -90,11 +90,15 @@ class GuestRegistrationServlet(DirectServeJsonResource):
 
                 device_id, access_token, _, _ = await self._api.register_device(user_id)
             else:
-                logger.info("Registering MAS guest user with username '%s'", localpart)
-                mas_user_id = await self._mas_admin_client.create_user(localpart)
+                logger.info("Registering MAS guest user with localpart '%s'", localpart)
 
+                # This will be the MAS-specific user ID (i.e. "01KFNJEB720EAGR907PSXRXQ51")
+                mas_user_id = await self._mas_admin_client.create_user(localpart)
+                # This is the Matrix user ID (i.e. "@guest_abc123:matrix.org")
                 user_id = self._api.get_qualified_user_id(localpart)
 
+                logger.info(f"Registered guest user: '{user_id}' (MAS ID: '{mas_user_id}')")
+
                 await self._api.set_displayname(
                     UserID.from_string(user_id),
                     displayname + self._config.display_name_suffix,