German Umlaute with Lazarus

Data Abstract
6

this is problem in fpc itself.
this simple testcase will fail:

program a;
{$MODE DELPHI}
uses
  SysUtils, DB, memds;
var
  mem: TMemDataset;
  str, fld: WideString;
  s: string;
begin
  str := widechar(#$00E4) + widechar(#$00F6) + widechar(#$00FC); //   'äöü';
  mem := TMemDataset.Create(nil);
  try
    mem.FieldDefs.Add('fld1', ftWideString, 20);
    mem.Open;
    mem.Insert;
    mem.fields[0].asWideString := str;
    mem.post;
    fld := mem.fields[0].AsWideString;
    if fld <> str then s := 'test is failed'  else  s := 'test is passed';
    writeln(s);
  finally
    mem.Free;
  end;
end.