Trigger error

Hello, i'm trying to create check trigger between two columns. But get query error. Structure of columns is: `start_t` (time) , `end_t` (time) The goal is hours in `end_t` don't be same with `start_t` (e.g. 11:00 > 11:00)

Here is query code:

CREATE TRIGGER `check_times` BEFORE INSERT ON `schedule` FOR EACH ROW
BEGIN
DECLARE v_end_time time;
SELECT end_t INTO v_end_time FROM `schedule` WHERE fn_stud = NEW.fn_stud;
IF NEW.start_t > v_end_time THEN SET NEW.fn_stud = NULL;
END IF;
END; 

MySQL says: #1064 - 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 '' at line 1

Don't understand what is wrong. Can anyone explain? Thanks.