SQL & PL/SQL

I am using 12.1.0.2

I want to create a procedure that takes 1 date parameter with default sysdate. even if NULL is passed I want to treat it as sysdate.  

create or replace  procedure proc1(p_date date default sysdate)

as

begin

dbms_output.put_line(p_date)

end proc1;

exec proc1; -- > should return sysdate

exec proc1(NULL); --> should return sysdate

Is it possible to do it  in procedure declaration or do I have to  use NVL within body?

Thanks