redux error on the property 'type' while using middlewares

Question

I'm trying to integrate a logger in my redux app, using the applyMiddleware api, but when I trigger an action I got this error:

Actions may not have an undefined "type" property. Have you misspelled a constant?

This is strange because all of my action creators returns objects with this format: { type : ..., payload : {...}}. And more, in the console of the browser the printed object has the property 'type'.

I set up the store in this way:

const logger = store => next => action => {
    console.log(action);
    return next(store, action);
}

const store = createStore(
    reducer,
    applyMiddleware(logger));

export default store;

I got stuck.