React cannot read property map of undefined

I am very new to react and I am trying to bring in data from a rails api but I am getting the error TypeError: Cannot read property 'map' of undefined

If i use the react dev tools I can see the state and I can see the contacts if I mess around with it in the console using $r.state.contacts Can someone help with what I have done wrong? my component looks like this:

import React from 'react';
import Contact from './Contact';

class ContactsList extends React.Component {
  constructor(props) {
    super(props)
    this.state = {}
  }

  componentDidMount() {
    return fetch('http://localhost:3000/contacts')
      .then(response => response.json())
      .then(response => {
        this.setState({
          contacts: response.contacts
        })
      })
      .catch(error => {
        console.error(error)
      })
  }

  render(){
    return(
     <ul>
        {this.state.contacts.map(contact => { return <Contact contact{contact} />})}
      </ul>
    )
  }
}

export default ContactsList;