CREATE TRIGGER fails with ER_EVENT_STORE_FAILED after unrelated failed ALTER

CREATE TABLE t1 (v ENUM('a','b'));

INSERT INTO t1 VALUES ('a'),('b');

--error WARN_DATA_TRUNCATED

ALTER TABLE t1 MODIFY COLUMN v ENUM('c','d');

CREATE TRIGGER trg AFTER STARTUP SET @x = 1;

DROP TABLE t1;

 query 'CREATE TRIGGER trg AFTER STARTUP SET @x = 1' failed: ER_EVENT_STORE_FAILED (1538): Failed to store event on_completion. Error code 1 "Operation not permitted" from storage engine