react-native: Warning: Failed child context type: Invalid child context `virtualizedCell.cellKey` of type `number` supplied to `CellRenderer`, expected `string`.

Getting the below warning when I use FlatList and where keyExtractor returns a number.

Warning: Failed child context type: Invalid child context `virtualizedCell.cellKey` of type `number` supplied to `CellRenderer`, expected `string`.
    in CellRenderer (created by VirtualizedList)
    in RCTScrollContentView (created by ScrollView)
    in RCTScrollView (created by ScrollView)
    in ScrollView (created by VirtualizedList)
    in VirtualizedList (created by FlatList)

Sample Code for reproduction

import React, { Component } from 'react';
import { Text, View, FlatList } from 'react-native';

export default class NotificationSettingsScreen extends Component {
  render() {
    return (
      <View style={{flex: 1, paddingTop: 36}}>
        <FlatList
          data={[1, 2, 3, 4, 5]}
          renderItem={({item}) => (
            <View>
              <Text>{item}</Text>
            </View>
          )}
          keyExtractor={(item) => item }
        />
      </View>
    );
  }
}

NOTE: Changing keyExtractor={(item) => item.toString()} makes this warning disappear.

Environment

React-Native: 0.53.0, react: 16.2.0

Expected Behavior

keyExtractor of FlatList must accept number instead of just string

Actual Behavior

Warning when using keyExtractor which returns number

Steps to Reproduce

Check above lines

The above problem could also be due to this commit https://github.com/facebook/react-native/commit/a010a0cebd4afc0d88336c2c265a5d9dbb19918f but not sure …