PLS-00215: String length constraints must be in range (1 .. 32767)

create or replace procedure tq84_pls_00215(txt varchar2) -- << This is ok
   authid definer
as
   txt_out varchar2;                                     -- << This throws PLS-00215: String length constraints must be in range (1 .. 32767)
begin
   txt_out := upper(txt);
   dbms_output.put_line(txt);
end tq84_pls_00215;
/