Petapoco nullable date return null even if table have value

Question

I am using petaPoco as my ORM.

Can you please tell me why this returns a null for a nullable date field even though it holds a valid date in the table. I am new to ORM and C#

employee emp = db.SingleOrDefault<employee>(
       "SELECT * FROM tbl_employee WHERE id=@0", Id
       );

Thanks

Edit :

My table schema

 CREATE TABLE `tbl_employee` (
`Id` INT(11) NOT NULL AUTO_INCREMENT,
`Name` VARCHAR(60) NOT NULL,
`Sex` VARCHAR(6) NOT NULL DEFAULT '0',
`dob` DATE NOT NULL COMMENT 'Date of Birth',
`DOJ` DATE NULL DEFAULT NULL COMMENT 'Date of join',
`Bank_ac_no` VARCHAR(20) NULL DEFAULT NULL,
`PAN_CARD_NO` VARCHAR(20) NOT NULL DEFAULT '',
`Home_Branch_ID` INT(11) NULL DEFAULT NULL,
`designation_id` INT(11) NULL DEFAULT NULL,
`Probationary_period` INT(11) NOT NULL DEFAULT '0' COMMENT 'Probationary Period in days',
`Appointment_refno` VARCHAR(15) NULL DEFAULT NULL,
`PF_Branch_ID` INT(11) NULL DEFAULT NULL COMMENT 'Branch _ID of the PF to be submitted',
`resigned` TINYINT(4) NOT NULL DEFAULT '0',
`mgrallowance` DOUBLE(15,2) NULL DEFAULT '0.00',
`comm_coef` DOUBLE(15,2) NOT NULL DEFAULT '1.00',
`emp_com_type` INT(11) NOT NULL DEFAULT '0'  ,
`Office_staff` INT(11) NULL DEFAULT '0',
`UID` VARCHAR(15) NULL DEFAULT '',
`desig_id` INT(11) NULL DEFAULT NULL,
`Working_branch_id` INT(11) NULL DEFAULT NULL,
`Rating` DOUBLE(10,2) NULL DEFAULT NULL,
`internal_ref_id` INT(11) NULL DEFAULT NULL ,
`approval_status` INT(11) NULL DEFAULT NULL,
`approved_id` INT(11) NULL DEFAULT NULL,
PRIMARY KEY (`Id`),
INDEX `desig_id` (`desig_id`)
 )
COLLATE='latin1_swedish_ci'
ENGINE=InnoDB
AUTO_INCREMENT=5054;

I am using MYSQL 5.5 and Mysql.Data 6.5.4 poco : https://www.yousendit.com/download/WUJaTXRkOW5oeVpvSWNUQw