Putting interfaces in a List

I'm an experienced programmer, but I'm working on my first Delphi project, and I've run into what seems to be a simple misunderstanding on my part.

Here is a snippet of the code. I am unable to insert Objects implementing the ITimeListener interface into a TObjectList. Retrieving the objects is ugly, and so I guess I am doing something wrong.

Do I just misunderstand what interfaces are in Delphi?

//===============================================
interface
    TExternalTimer = class(TInterfacedObject, ITimeListener)
    private
        mListeners: TObjectList;
    protected
        procedure OnCorrectedTimeEvent(Bib: String; Channel: Integer; Time: TRaceTime);
    public
        procedure RegisterListener(Listener: ITimeListener);
    end;

implementation
procedure TExternalTimer.OnCorrectedTimeEvent(Bib: String; Channel: Integer; Time: TRaceTime);
var
    I: Integer;
begin
    for I := 0 to (mListeners.Count - 1) do
        begin
        ((mListeners[I] as TInterfacedObject) as ITimeListener)
            .OnCorrectedTimeEvent(Bib, Channel, Time);
        end;
end;

procedure TExternalTimer.RegisterListener(Listener: ITimeListener);
begin
    // This complains that I TObject and ITimeListener are incompatible.
    mListeners.Add(Listener);
end;
//===============================================

From what I've seen, Delphi doesn't seem to treat interfaces as a "view" into some concrete object. They are a different beast altogether and that, I think, is what's making my head hurt.