Unexpected ER_NON_UPDATABLE_TABLE upon executing trigger

CREATE TABLE t1 (f INT);

CREATE TABLE t2 (a INT);

CREATE VIEW v AS SELECT 'x' UNION SELECT 'x' UNION SELECT 'x';

CREATE TRIGGER tr BEFORE INSERT ON t1 FOR EACH ROW DELETE FROM v;

--error ER_NON_UPDATABLE_TABLE

INSERT INTO t1 VALUES (1);

DROP VIEW v;

CREATE VIEW v AS SELECT * FROM t2;

INSERT INTO t1 VALUES (2);

DROP VIEW v;

DROP TABLE t1, t2;

mysqltest: At line 9: query 'INSERT INTO t1 VALUES (2)' failed: ER_NON_UPDATABLE_TABLE (1288): The target table v of the DELETE is not updatable