Failure at second executon of PS for query using stored function

CREATE TABLE t1 (a INT,b INT);

INSERT INTO t1 VALUES (10,1),(20,2),(30,3),(40,4);

CREATE VIEW v1 AS

SELECT a,1 as b FROM t1 WHERE a>(SELECT AVG(a) FROM t1 t) AND b>(SELECT 1);

DELIMITER |;

CREATE FUNCTION f1() RETURNS INT

BEGIN

  DECLARE a TYPE OF v1.a DEFAULT 10;

  RETURN a+1;

END;

|

DELIMITER ;|

PREPARE stmt FROM "SELECT f1();";

EXECUTE stmt;

EXECUTE stmt;

DEALLOCATE PREPARE stmt;

DROP FUNCTION f1;

DROP VIEW v1;

DROP TABLE t1;