Linking Custom Fields on the ask a question page on the customer portal page

I have created two custom field on the incident workspace on the agent side, i want to add them on the customer portal on the ask a question page.

Am having the below error on the side of the ask a question page

error

Widget Error: standard/input/FormInput - County field doesn't exist on the Incident primary object

Code on the ask.php

<rn:widget path="input/FormInput" name="Incident.county" required="true" initial_focus="true" />