Invalid default value for 'RET_DATE'

I created a db table named LOAN and I encountered error after executing this query.

CREATE TABLE LOAN
(
	`L_ID` INTEGER not null PRIMARY KEY,
	`BORROWER` INTEGER not null,
	`BOOK` 	INTEGER not null,
	`ISSUER` INTEGER not null,
	`ISS_DATE` TIMESTAMP not null,
	`RECEIVER` INTEGER ,
	`RET_DATE` TIMESTAMP ,
	`FINE_PAID` BOOLEAN	
);