Bogus error for query with two usage of CTE referring another CTE

CREATE TABLE t1 (id INT(10) NOT NULL AUTO_INCREMENT PRIMARY KEY);

/* Generate 10'000 entries */

INSERT INTO t1(id) SELECT @row := @row + 1 AS id FROM 

(SELECT 0 UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) t,

(SELECT 0 UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) t2, 

(SELECT 0 UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) t3, 

(SELECT 0 UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) t4, 

(SELECT @row:=0) numbers;

CREATE OR REPLACE FUNCTION check_my_id(in_id INT) RETURNS INTEGER

READS SQL DATA

RETURN (SELECT id FROM t1 WHERE t1.id = in_id);

WITH c1 AS (SELECT id	FROM t1 a WHERE check_my_id(id) = id GROUP BY id),

	   c2 AS (SELECT pt.id FROM c1 pt GROUP BY pt.id)

SELECT id FROM c2 GROUP BY id

UNION ALL

SELECT id FROM c2;