Node of kind optional is not valid as a required definition

Hello! Whenever I use a type with an optional key with a default value like this:

const def = type({
    'agree?': 'boolean = true',
})

const def = type({
    'agree?': 'boolean = true',
})

I get the error

Node of kind optional is not valid as a required definition

Node of kind optional is not valid as a required definition

. What could it mean? Note that I'm also updating the

type

type

via

map

map

, but removing that mapping appeared to have no effect so far.

Removing the default value throws no error