Setting a default value in Scala/Slick

Question

I'm trying to persist data with Scala/Slick in play framework. I'm sending a request via json and I'm trying to validate said request by matching it to a model like this:

request.body.asJson.map(_.validate[Foo] match {...}

The question is: How do I set a default column value (to false)?

This is my evolution file:

CREATE TABLE Foo(
    ...
    deleted BOOLEAN NOT NULL DEFAULT FALSE,
    ...
)

This is my model (.scala):

case class Foo(
                    ...
                    deleted: Boolean,
                    ...)

This is my dao (.scala):

 class Foo(tag: Tag) extends TableFoo(tag, "Foo"){
            ...
                def deleted = column[Boolean]("deleted", O.Default(false))
            ...

                def * = (..., deleted, ...) <> ((Foo.apply _).tupled, Foo.unapply)
        }

The problem occurs while validating the request to the model. When defining deleted as Option[Boolean], it writes None/Null for the column deleted. When defining it as Boolean, the validation fails. Presumably, because the request is missing the attribute deleted.

Why defining a default value, when the validation fails after all or in the case of Option[Boolean] just writes None/Null? Is there an easy way to set a reliable default value in Scala/Slick or Evolutions?