[Lazarus] Hello World program generates a File Not Open runtime error

[Antônio]

program project1;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes
  { you can add units after this };

begin
  WriteLn('Hello World');
  ReadLn();
end.

Any problem? Am I missing something?