How to save an object in redux?

I build an app in React with Redux and I try to send to my state an object and I try to save it in ‘thisUser’ but I don’t know how to write that ‘return’ because mine doesn’t work.

My Redux state:

const initialState = {
    thisUser: {}
}

export function usersReducer(state = initialState, action) {
    switch (action.type) {
        case 'users/addUser':
            return { ...state, thisUser: { ...state.thisUser, ...action.payload} }  //the problem
        default:
            return state
    }
}

Dispatch method:

dispatch({ type: "users/addUser", payload: new_user });

Can you tell me how to write that return, please?