How to tell if a folder exists with IdFTP delphi?

I need to know if a folder exists on ftp

I'm using the function below, but the error:

---------------------------
Debugger Exception Notification
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Project perfil.exe raised exception class EIdReplyRFCError with message 'Directory not found.
'.
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Break   Continue   Help   
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The function I'm using is this:

function FTPFileExists(aFileName: string): Boolean;
begin
  try
    fdm.IdFTP.List(nil, aFileName, False);
    Result := (fdm.IdFTP.ListResult.Count > 0);
  except
    Result := False;
  end;
end;

fdm is my datamodule and IdFTP the Indy component delphi is Xe6