unset a profile option with rest?

I know how to set an option in the ssl client profile to a non-default value using iControl REST, name it and provide an acceptable value:

{"name":"/Common/cw2","sslSignHash":"sha256"}

But what if I want to stop using a special per-profile value in this ssl client profile and use the default from the parent's value instead? The idea is to clean up a bunch of profiles and manage a parameter in the parent.

This gives me an error:

{"name":"/Common/cw2","sslSignHash":null}

{
   "errorStack" : [],
   "message" : "invalid property value \"ssl-sign-hash\":\"none\"",
   "code" : 400
}

I've tried with "disabled", 0, "default" and a stack of other things. No matter what, the gui shows that I'm overriding the parent.

The 11.5 tmsh reference just says that the default for the example parameter is "Any", but I can't find where it says how to remove an option from a profile.

Have any of you done this and would you mind sharing some hints?