关于laravel5迁移数据库报错的问题

运行了php artisan migrate后报错

SQLSTATE[42000]: Syntax error or access violation: 1067 Invalid default val
ue for 'created_at' (SQL: create table

users

(

id

int unsigned not null
auto_increment primary key,

name

varchar(255) not null,

email

varchar(2
55) not null,

password

varchar(60) not null,

remember_token

varchar(100
) null,

created_at

timestamp default 0 not null,

updated_at

timestamp d
efault 0 not null) default character set utf8 collate utf8_unicode_ci)

不知道是什么问题??