HTTP post to a form to clear a contact property


We need to know what we are doing wrong when posting to an HubSpot form trying to clear a contact property.
Can someone explain to us how a property that shall be cleared should look like in the format “Content Type: application/x-www-form-urlencoded”.

We are trying to post the following values to clear the property named “LicenseExpirationDate”

Value: null

Value: "null"

Value: ""

What value are we supposed to post? the above examples does not appear to work.


@Norlander You can use this endpoint here to update a contact property.