MySQL Stored Procedure Parameters are NULL

I am stumped, and was hoping someone here would have a quick and easy answer. I did a fresh install of MySQL 5.5 and am trying to pass parameters into a stored procedure. The parameter values aren't being read by the stored procedure. MySQL doesn't throw an error and processes the code with null parameters. Here is the code:

DELIMITER $$

CREATE DEFINER=`root`@`%` PROCEDURE `testing`(IN parameter INTEGER)
BEGIN
    UPDATE table_name SET valueToChange = 'Test' WHERE mainID = @parameter;
END

And here is the query I'm using to call it:

USE database_name; CALL testing(72);

Can anyone help?