Singleton

Ifølge http://community.borland.com/article/0,1410,22576,00.html
skulle denne implementation af en singleton virke.

Men jeg får en fejl i denne linje:
Instance := inherited NewInstance;
[Error] SingletonUnit.pas(36): Incompatible types: 'TSingleton' and 'TObject'


unit SingletonUnit;

interface

type
  TSingleton = class
  public
    class function NewInstance: TObject; override;
    procedure FreeInstance; override;
    class function RefCount: Integer;
  end;

implementation

{ TSingleton }

var
  Instance  : TSingleton  = nil;
  Ref_Count : Integer    = 0;

procedure TSingleton.FreeInstance;
begin
  Dec( Ref_Count );
  if ( Ref_Count = 0 ) then
  begin
    Instance := nil;
    // Destroy private variables here
    inherited FreeInstance;
  end;
end;

class function TSingleton.NewInstance: TObject;
begin
  if ( not Assigned( Instance ) ) then
  begin
    Instance := inherited NewInstance;
    // Initialize private variables here, like this:
    //  TSingleton(Result).Variable := Value;
  end;
  Result := Instance
  Inc( Ref_Count );
end;

class function TSingleton.RefCount: Integer;
begin
  Result := Ref_Count;
end;

end.


jeg fårstår ikke fejlen da TSingleton jo er af typen 'TObject'.
Nogen som kan hjælpe?