Anyone here know why this code is not working?

let users = {

  Alan: {

    age: 27,

    online: false

  },

  Jeff: {

    age: 32,

    online: true

  },

  Sarah: {

    age: 48,

    online: false

  },

  Ryan: {

    age: 19,

    online: true

  }

};



function countOnline(obj) {

  // change code below this line

  let onlineUsers = 0;

  for (let user in users) {

    if (user.online) {

      onlineUsers += 1;

    }; 

  };

  return onlineUsers;

  // change code above this line

}



console.log(countOnline(users));