How to refactor/rename Redux state shape when users already have locally persisted stores?

I have a React Native mobile app which uses Redux and redux-persist.

Suppose the state shape currently looks like this:

notifications: {
    new_messages: 2,
    new_friend_requests: 0,
    new_jobs: 0
}

Suppose that we currently set those values with 1 reducer, where action.notifications is a dictionary with keys new_messages, new_friend_requests, and new_jobs.

const notifications = (state = {}, action) => {
  switch (action.type) {
    case SET_NOTIFICATIONS: 
      return action.notifications;
    default:
      return state;
  }
}

I would like to

1. get rid of new_jobs, since it is no longer relevant
2. split the reducer
3. rename new_friend_requests to new_friend_requests_count
4. rename new_messages to new_messages_count

The new state shape would look like this:

notifications: {
    new_messages_count: 2,
    new_friend_requests_count: 0
}

And we would have new reducers

const new_messages_count = (state = {}, action) => {
  switch (action.type) {
    case SET_NEW_MESSAGES: 
      return action.new_messages_count;
    default:
      return state;
  }
}

const new_friend_requests_count = (state = {}, action) => {
  switch (action.type) {
    case SET_CONNECTION_REQUESTS: 
      return action.new_friend_requests_count;
    default:
      return state;
  }
}

const notifications = combineReducers({
  new_messages_count,
  new_friend_requests_count
});

However, when I make that change, I run into an error message like this:

Unexpected keys "new_messages", "new_friend_requests", "new_jobs" found in previous state received by the reducer. Expected to find one of the known reducer keys instead: "new_messages_count", "new_friend_requests_count". Unexpected keys will be ignored.

I understand why this happens: the user's previously persisted redux state contains those keys, and that gets rehydrated into my new Redux state shape. My question is, what is a graceful way to handle this situation?

EDIT: I realized that the error message may be entirely due to renaming the variables, and that the reducer split/decomposition may not be relevant. Still, how would you gracefully rename those variables without running into that error?