Clave primaria compuesta me devuelve error

[ramondevesa]

Código MySQL:

CREATE TABLE `plaali` ( 
`id_alimentos` int(11) NOT NULL, 
`id_plato` int(11) NOT NULL, 
`cantidad` int(4) DEFAULT NULL, 
PRIMARY KEY (`id_alimentos`,`id_plato`), 
KEY `plaali_plato` (`id_plato`), 
CONSTRAINT `plaali_alimentos` FOREIGN KEY (`id_alimentos`) REFERENCES `alimentos` (`id`), 
CONSTRAINT `plaali_plato` FOREIGN KEY (`id_plato`) REFERENCES `plato` (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8