Delphi REST.JSON TJson.JsonToObject Problem with inheritance

I would like to use the REST.JSON Librairy to convert an Object to a JSON-String and back, but i'm encountering some problems.

Let's say the classes i would like to convert is "TFooChild1" and "TFooChild2" which both descend from "TFoo". The classes look like this:

TFoo = class
protected
  Name: string;
  Value: Double;
end;

TFooChild1 = class(TFoo)
private
  Limit: Double;
end;

TFooChild2 = class(TFoo)
private
  Limit: Double;
  WorkerID: Integer;
end;

Creating and converting to JSON would look something like this:

var
  Foo: TFoo;
  s: string;
begin
  Foo := TFooChild1.Create;
  Foo.Name:= '...';
  ... //assign all the Fields
  s := TJson.ObjectToJsonString(Foo);
  Foo.Free;

  //conversion to string is correct...

  Foo := TJson.JsonToObject<TFoo>(s, []);
  //Field "Limit" is lost
end

I'm aware that this (TJson.JsonToObject<TFoo>(s, [])) would never return the type TFooChild1, but that's exactly what i need.

When you convert back to an Object, the Fields of the child classes are lost. How do I avoid this? I can't do JsonToObject<TFooChild1> because I don't know if it's gonna be Child1 or Child2. Any hints?

I've googled if there's maybe a ConvertOption that would include Type information, but i haven't found anything