Informix 11.7 - procedure alter sequence restart dynamically

Hi

I'm facing a problem creating a procedure doing exactly what is in the subject.
Basically what I would like to do is :

alter sequence my_sequence RESTART select max(my_id) from mytable;

But I figured it can't be that simple. Indeed this doesn't work. So I made a simple procedure :

CREATE PROCEDURE upd_my_seq()

DEFINE max_my_id DECIMAL(19,0);
SELECT MAX(my_id) INTO max_my_id FROM my_table;
ALTER SEQUENCE my_sequence RESTART max_my_id;

END PROCEDURE ;

Unfortunately it didn't work either (procedure compiling error):
201: A syntax error has occurred.

Eventually I managed to compile a correct and more sophisticated procedure :

CREATE PROCEDURE upd_my_seq()

DEFINE max_my_id INTEGER;
DEFINE req VARCHAR;

SELECT MAX(my_id) INTO max_my_id FROM my_table;
LET req = "ALTER SEQUENCE my_sequence RESTART ?";
PREPARE prep_req FROM req;
DECLARE cur_maxid CURSOR FOR prep_req;
OPEN cur_maxid USING max_my_id;
FETCH prep_req;

END PROCEDURE;

Now this procedure compiles ok. But once again I have an error when executing the procedure :
201: A syntax error has occurred. :confused:

Does anyone has an idea ?

Thanks