MySQL foreign key ON DELETE SET NULL check data types error

MySQL foreign key ON DELETE SET NULL check data types error

I'm working on a normalised database, to be secure I wanted to use foreign
keys.
My database:
CREATE TABLE `names` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(250) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `name` (`name`),
KEY `name_2` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
CREATE TABLE `users` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name_id` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `name_id` (`name_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
The command:
ALTER TABLE `names` ADD FOREIGN KEY ( `name` ) REFERENCES `temp`.`users` (
`name_id`
) ON DELETE SET NULL ON UPDATE CASCADE ;
The response (error):
Error creating foreign key on name (check data types)
So, how to fix this?
Thanks