Inheritance problem when saving to prefab

I'm having some problem with inheritance, when saving it to prefabs.

I have two classes:

class A { public virtual void Call() { Debug.Log("Hello A"); } }

class B : A { public override void Call() { Debug.Log("Hello B"); } }

I then create an empty prefab, create a game object, add a simple script to hold my object of type B, and lastly replace the prefab with my game object (all done with a script).

The simple script will in Awake do this: someObj.Call();

If I do this on runtime. That is create empty prefab, and so on. Then it will output: "Hello B".

If I do this on editortime, and then add the created prefab to the scene. Then it will output: "Hello A".

So my question is: How do I get around this problem, without creating several lists for each type?