Error calling a stored procedure in MariadDB

Hi

I have MariaDB running on Linux. I have created a stored procedure:

DELIMITER //
CREATE DEFINER=`root`@`%` PROCEDURE `UpdatePeriodLocaltime`(IN `startUtcTime` datetime, IN `tableName` VARCHAR(50))
BEGIN
DECLARE period, localperiod, startrange, endrange datetime;
declare _offset time;
declare endtime datetime;
declare _dstStart, _dstEnd date;
declare statement varchar(256);


SET period = startUtcTime;

set endtime = addtime(startUtcTime,'1 00:15:00');

select offset, dstStart, dstEnd from timezone into _offset, _dstStart, _dstEnd;

if (startUtcTime >= _dstStart and startUtcTime < _dstEnd) then
set _offset = addtime(_offset, '01:00:00');
end if;


periods_loop : LOOP

IF period >= endtime

THEN leave periods_loop;

END IF;

set localperiod = addtime(period, _offset);
set startrange = addtime(period, '-00:07:30');
set endrange = addtime(period,'00:07:30');


UPDATE updperiod SET timest = period;

set @sql = concat('update ', tableName, ' set periodlocaltime = "', localperiod, '" where starttime > "', startrange, '" and starttime <= "', endrange, '"');

#UPDATE pre_mib2 SET periodlocaltime = addtime(period, _offset) WHERE starttime > (addtime(period, '-00:07:30')) AND starttime <= (addtime(period,'00:07:30'));

prepare stmt1 from @sql;
execute stmt1;
deallocate prepare stmt1;



set period = addtime(period, '00:15:00');


END loop;


END//
DELIMITER ;

But when I try to call the procedure I get the following error:

mysql> call UpdatePeriodLocaltime("2015-04-02","table_name");
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'NULL' at line 1


I have created another procedure with only one IN parameter and that works just fine...

What am I missing here?

P