problems with unordered map

I guess there's a problem with the optimizer.
Try the following code:

import module namespace map = "http://www.zorba-xquery.com/modules/store/data-structures/unordered-map";

declare namespace ann = "http://www.zorba-xquery.com/annotations";
declare variable $local:processed-internal-links := xs:QName("processed-internal-links");

declare %ann:sequential function local:f1($n as xs:string)
{
  map:insert($local:processed-internal-links, $n, $n);
  fn:trace($n, "n=");

  for $x in ("1", "2", "3")
  return
    if(fn:empty(map:get($local:processed-internal-links, $x))) then
      local:f1($x)
    else
      ()
};

map:create($local:processed-internal-links, xs:QName("xs:string"));

local:f1("0")

It should display 0 1 2 3
But it displays 0 1 2 3 3 2 3