TypeError: items.map is not a function

I made a request in a URL via Fetch, however it returns an error when I request json mapping, does anyone know how to solve it?

I've hidden the URL because it's private.

import React, { Component } from 'react';


class App extends Component {
 constructor(props){
 super(props);
 this.state = {
 items:[],
 isLoaded: false,
 }
 }

componentDidMount(){
fetch('***')
  .then(res => res.json())
  .then(json => { 
    this.setState({
      isLoaded: true,
      items : json,
    })
  });
 }

render() {

var{isLoaded, items} = this.state;

if(!isLoaded){
  return <div>Loading..</div>
}
else{

return (
    <div className="App">
      <ul>
        {items.map(item => (
          <li key = {item.id}>
            Name : {item.name} | {item.name}
          </li>
        ))};
      </ul>    
    </div>
  );
 }
}

}

export default App;