MySQL Foreign key error 1215, even though both colums are of the same type and are NOT NULL - mysql

Question

Parent table team_entrant:
CREATE TABLE IF NOT EXISTS `team_entrant` (
`entrant_number` tinyint(4) NOT NULL,
`qualifying_position` tinyint(4) NOT NULL,
`qualifying_time` time(3) NOT NULL,
`grid_position` tinyint(4) DEFAULT NULL,
`best_race_time` datetime DEFAULT NULL,
`final_position` tinyint(4) DEFAULT NULL,
`dnf_reason` varchar(45) DEFAULT NULL,
`team_id` int(11) NOT NULL,
`competition_year` date NOT NULL,
PRIMARY KEY (`entrant_number`),
KEY `fk_team_entrant_team1_idx` (`team_id`),
CONSTRAINT `fk_team_entrant_team1` FOREIGN KEY (`team_id`) REFERENCES `team` (`team_id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Child table/Associative table entrant_drivers:
CREATE TABLE IF NOT EXISTS `entrant_drivers` (
`entrant_number` tinyint(4) NOT NULL,
`competition_year` date NOT NULL,
`driver_id` int(11) NOT NULL,
PRIMARY KEY (`entrant_number`,`competition_year`,`driver_id`),
CONSTRAINT `ed_entrant_fk` FOREIGN KEY (`entrant_number`) REFERENCES `team_entrant` (`entrant_number`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
At the time the team_entrant column competition_year did not exist.
HeidiSQL refuses to execute the following code:
ALTER table entrant_drivers ADD CONSTRAINT ed_comp_year_fk FOREIGN KEY (competition_year) REFERENCES team_entrant(competition_year);
SQL Error (1215): Cannot add foreign key constraint
Extraneous table, driver involved with the associative table:
-- Dumping structure for table 99_lemans_db1.driver
CREATE TABLE IF NOT EXISTS `driver` (
`driver_id` int(11) NOT NULL,
`driver_name` varchar(64) NOT NULL,
`driver_nationality` varchar(32) NOT NULL,
`driver_birth_day` date NOT NULL,
`driver_best_previous_finish_class` varchar(8) DEFAULT NULL,
`driver_best_previous_finish_position` tinyint(4) DEFAULT NULL,
`team_entrant_id` int(11) NOT NULL,
PRIMARY KEY (`driver_id`,`team_entrant_id`),
KEY `fk_driver_team_entrant1_idx` (`team_entrant_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Any assistance would be appreciated.

Answer 1

The parent column must be designated as an index/primary key.
team_entrant is supposed to be made up of the composite primary keys (entrant number, competition year).