PHP artisan migrate --seed 出现问题，是因为版本问题？？

$ php artisan migrate --seed
Migration table created successfully.

[Illuminate\Database\QueryException]
SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 1000 bytes (SQL: al
ter table notifications add index notifications_notifiable_id_notifiable_type_index(notifiable_id, notifiable_type ))

[PDOException]
SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 1000 bytes