mysql – Error 1005 clave foranea SQL

Al intentar crear la clave for├ínea me da error 1005 can’t create table matricula

tabla matricula

CREATE TABLE `matricula` (
`cod_matricula` varchar(45) NOT NULL,
`id_info_matricula` int(11) NOT NULL,
PRIMARY KEY (`cod_matricula`),
FOREIGN KEY (`cod_matricula`) REFERENCES alumnos(`cod_matricula`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

tabla alumno

CREATE TABLE `alumno` (
`id` int(11) DEFAULT NULL,
`nombre` varchar(45) DEFAULT NULL,
`apellido` varchar(45) DEFAULT NULL,
`cod_matricula` varchar(45) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;