[racket] Bug in Algol 60 procedure calls

The Algol 60 language doesn't seem to work with procedures of no
arguments.  For example, the following works as expected:
begin
  integer procedure P(x);
  begin
     P := 3;
  end;
  printn(P(2));
end

But if I change P to take no arguments, I get an error:
begin
  integer procedure P;
  begin
     P := 3;
  end;
  printn(P);
end
printn: expected argument of type <number>; given #<procedure:tmp>

Is this a bug or am I doing something wrong?

Justin