PHP: WordPress wp_list_pluck error

wp_list_pluck.php

<?php
// Create objects
$obj1 = $obj2 = new stdClass();
$obj1->slug = 'slug-1';
$obj1->name = 'Slug 1';
$obj2->slug = 'slug-2';
$obj2->name = 'Slug 2';

// Create array
$array_of_objects = array( $obj1, $obj2 );

// Test
$list = wp_list_pluck( $array_of_objects, 'ID' );

// Alternate
if ( $list = wp_list_pluck( $array_of_objects, 'ID' ) ) {
  //do something
}

/*
Result:
Notice: Undefined property: stdClass::$ID in /srv/www/trunk/htdocs/wp-includes/functions.php on line 3209
*/