const
   WM_CLSYNCHRONIZE = WM_USER + 1;
...
type
   TActiveFormX = class(TActiveForm, IActiveFormX)
      procedure WMclSynchronize(var Message: TMessage);
      message WM_CLSYNCHRONIZE;
...
procedure TActiveFormX.ActiveFormCreate(Sender: TObject);
begin
   Classes.WakeMainThread := DoOnWakeMainThread;
end;

procedure TActiveFormX.DoOnWakeMainThread(Sender: TObject);
begin
   PostMessage(Self.Handle, WM_CLSYNCHRONIZE, 0, 0);
end;

procedure TActiveFormX.WMclSynchronize(var Message: TMessage);
begin
   Classes.CheckSynchronize();
end;