SQL - nefunguje foreign key

CREATE TABLE `permissions` (
    `id_function` int(3) unsigned NOT NULL AUTO_INCREMENT,
    `function` varchar(32) NOT NULL,
    `create_acc` tinyint(1) NOT NULL DEFAULT '0',
    `edit_acc` tinyint(1) NOT NULL DEFAULT '0', 
    `delete_acc` tinyint(1) NOT NULL DEFAULT '0',
    `add_firm` tinyint(1) NOT NULL DEFAULT '0', 
    `edit_firm` tinyint(1) NOT NULL DEFAULT '0', 
    `delete_firm` tinyint(1) NOT NULL DEFAULT '0', 
    `add_item` tinyint(1) NOT NULL DEFAULT '0', 
    `edit_item` tinyint(1) NOT NULL DEFAULT '0', 
    `delete_item` tinyint(1) NOT NULL DEFAULT '0', 
    `add_product` tinyint(1) NOT NULL DEFAULT '0',
    `edit_product` tinyint(1) NOT NULL DEFAULT '0',
    `delete_product` tinyint(1) NOT NULL DEFAULT '0',
    `view_type` varchar(32) DEFAULT NULL, 
    `view_acc` tinyint(1) NOT NULL DEFAULT '0', 
    `log` tinyint(1) NOT NULL DEFAULT '0',
    `superadmin` tinyint(1) NOT NULL DEFAULT '0',
    `note` varchar(256) DEFAULT NULL,
    PRIMARY KEY (id_function),
    UNIQUE (function)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

/* create functions */
INSERT INTO permissions (id_function, function, create_acc, edit_acc, delete_acc, add_firm, edit_firm, delete_firm, add_item, edit_item, delete_item, add_product, edit_product, delete_product, view_type, view_acc, log, superadmin, note) VALUES
(1,'Superadmin',1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,'Superadmin, nejvyšši autorita, může být měněn pouze ručně v DB, právo na vše'),
(2,'Admin',1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,'Administrátor, stará se o funkci webu');



CREATE TABLE `accounts` (
    `id` int(3) unsigned NOT NULL AUTO_INCREMENT,
    `name` varchar(64) NOT NULL,
    `surname` varchar(64) NOT NULL,
    `mail` varchar(64) NOT NULL,
    `password` varchar(256) NOT NULL,
    `permissions` int(3) NOT NULL,
    PRIMARY KEY (id),
    UNIQUE (mail),
    FOREIGN KEY (permissions) REFERENCES permissions(id_function)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;