Mobx-state-tree SSR double init client and server

I use mobx-state-tree on my NextJS app with Server Side Rendering. On the server only, I fetch an API to load some information and add to my Store. But after the client load, my store is cleared because I need to instantiate on server AND client. That's my problem.

My store :

const Store = types
  .model('Store', {
    user: types.compose(User),
  });

const createStore = Store.create({
  user: {},
});

let store = null;

/**
 * Init store
 *
 * @param {bool} isServer
 * @param {object} snapshot
 */
const initStore = (isServer, snapshot = null) => {

  if (isServer) {
    store = createStore;
  }

  if (store === null) {
    store = createStore;
  }

  if (snapshot) {
    applySnapshot(store, snapshot);
  }

  return store;
};

My component on client side :

  static getInitialProps({ req }) {
    const isServer = !!req;
    const store = initStore(isServer);

    return { initialState: getSnapshot(store), isServer }
  }

  constructor(props) {
    super(props);
    this.store = initStore(props.isServer, props.initialState);
  }

And my User store :

const User = types
  .model('User', {
    name: types.optional(types.string, ''),
    first_name: types.optional(types.string, ''),
  })
  .actions(self => {

    function load(name) {
      self.name = name;
    };

    async function afterCreate() {
      if (IS_SERVER) {
        const request = await callApi();
        return self.load(request.user.name);
      }
    };

    return {
      load,
      afterCreate
    };

  })
  .views(self => ({
    get userName() {
      return self.name;
    },
  }));

My actions self.load(name) is working but removed on client sideloaded.

Anyone know how I can "save" the user store from the server side?

Thank you!