Permission denied - geolocation in React Native

I've been playing around with React Native, getting custom locations to work and setting the "NSLocationWhenInUseUsageDescription" key. The error, when running on the ios simulator, is this:

{"code": 2,"message": "Unable to retrieve location.","PERMISSION_DENIED": 1,"POSITION_UNAVAILABLE": 2,"TIMEOUT": 3 }

This is what I have, pretty much straight from the Geolocation example page https://facebook.github.io/react-native/docs/geolocation.html

/* eslint no-console: 0 */'use strict';var React = require('react');var ReactNative = require('react-native');var {  StyleSheet,  Text,  View,} = ReactNative;export default class GeolocationExample extends React.Component {  state = {    initialPosition: 'unknown'  };  componentDidMount() {    navigator.geolocation.getCurrentPosition(      (position) => {        var initialPosition = JSON.stringify(position);        this.setState({initialPosition});      },      (error) => alert(JSON.stringify(error)),      {enableHighAccuracy: true, timeout: 20000, maximumAge: 1000}    );  }  render() {    return (<View><Text><Text style={styles.title}>Initial position: </Text>          {this.state.initialPosition}</Text></View>    );  }}var styles = StyleSheet.create({  title: {    fontWeight: '500',  },});

Any help would be appreciated!