Problem setting foreign key using phpmyadmin

[wisni1rr]

I currently have two tables: tblCustomer and tblOrders.
In tblCustomer I have a field CustomerID that was set with the SERIAL datatype and set as PRIMARY. In tblOrders I have the fields OrderID that was set with the SERIAL datatype and set as PRIMARY. I also have a field called CustomerID with the BIGINT(20) datatype. I am trying to create a foreign key on tblOrders.CustomerID to relate back to tblCustomer.CustomerID. All the data is InnoDB.

ALTER TABLE  `tblOrders` ADD FOREIGN KEY (  `CustomerID` ) REFERENCES  `Sample`.`tblCustomer` (
`CustomerID`
) ON DELETE CASCADE ON UPDATE CASCADE ;

I get an error of check datatypes. I'm not sure what I am doing wrong. Any Ideas?

[wisni1rr]

SOLVED

tblOrders.CustomerID was not set with the unsigned attribute as tblCustomer.CustomerID was.