Simple update query has strange characters in binary log

[kjcsb]

I have the following stored procedure:
DELIMITER $$

DROP PROCEDURE IF EXISTS `tool`.`sp_replicate` $$
CREATE PROCEDURE `sp_replicate`(IN HOST VARCHAR(45))
BEGIN
DECLARE LAST_ID, GREATEST_ID INT;
START TRANSACTION;
SELECT MAX(id) INTO GREATEST_ID FROM cdrdb.cdr;
UPDATE tool.replicate_track SET id = GREATEST_ID where host = HOST;
COMMIT;
END $$

DELIMITER ;

This is called using the following:
* * * * * mysql --user='call' --password='call' --execute="CALL tool.sp_replicate_asterisk_cdr(60)"

The following appears in the binary log:
UPDATE cdr.replicate_track SET id = NAME_CONST('GREATEST_ID',10353) where NAME_CONST('host',O #@pX
Ø$ð|XpX
ÈaÏ
Øa_latin1'60') = NAME_CONST('HOST',OÌÛ"hpX
Ø$b|XȺ. #ÈaÏ
Øa_latin1'60');

This is causing replication problems so I wondered how to avoid it. Is it character set related? Any advice would be appreciated. Note that I need to pass alphanumeric data to the stored procedure; enclosing the passed data in '' didn't help.