INSERT ON DUPLICATE KEY UPDATE produces error 1032 (Can't find record)

CREATE DATABASE `testdb`;

USE `testdb`;

CREATE TABLE `parent` (

    `id` INT PRIMARY KEY AUTO_INCREMENT

) ENGINE=INNODB;

CREATE TABLE `child` (

    -- crucial bit: FK has to be primary key (or if composite, at the start of the primary key)

    `parent_id` INT NOT NULL PRIMARY KEY,

    `id` INT NOT NULL,

    CONSTRAINT `fk_c_parent` FOREIGN KEY (`parent_id`) REFERENCES `parent`(`id`) ON UPDATE CASCADE ON DELETE CASCADE

) ENGINE=INNODB;

-- This works as expected, producing a 1452 error (foreign key constraint fails)

INSERT INTO `child` (`id`, `parent_id`) VALUES (1, 1);

-- ERROR 1032 (HY000): Can't find record in 'child'

INSERT INTO `child` (`id`, `parent_id`) VALUES (1, 1) ON DUPLICATE KEY UPDATE `id` = VALUES(`id`);