Loading from Redux storage does not overwrite initial state completely

Question

it seems that loading from the Redux storage does not overwrite the initial state completely, and that looks like a bug for me. ( If it's not, please tell me how I can work with it productively. :) )

An example: Let's say, this is my initial state:

state = {
  ...
  test: {
    foo: 1,
  }
  ...
}

Then, in some dispatch, I change the value of test:

nextState.test = { bar: 2 };

With redux-storage set up, this is saved (I guess).

When I now close/reopen or reload the whole app, I have this state:

state = {
  ...
  test: {
    bar: 2,
    foo: 1,
  }
  ...
}

I think, there should be no foo: 1 at this point, should it?

At least it's bugging me in my app, so what's the correct way of getting rid of it? Is there a config option for redux-storage that I can set?

(See the whole code here.)