How to persist nested object in same reducers.?

I am using redux-persist and I have nested object in a reducer like below

const initState = {
    ian: "initial value",
    details: {
        prop1: "inital value",
        prop2: "inital value"
    }
};

// Reducer (SomeReducer) create

const persistcnfg = {
    key: "SomeReducer",
    storage: storage
},

const rootReducer = combineReducers({
    someReducer: persistReducer(persistcnfg, SomeReducer)
});

I can see the changes save localstorgae, but when reload the page ian value is updated one, but details value reset to the intialState. How I can persist nested object too.