$M+ what´s up with this directive

[wluis]

i was installed the indy 10.2.0.3, now i´need know what happen with this error
Only classes which are compiled in $M+ mode can be published

i´ve this

type
  TdmWMSClient = class(TDataModule)

   xmlDoc: TXMLDocument;

    // a TIdHTTP object

    httpClient: TIdHTTP; // the error it´s here
  private
  
   
  protected
  
  public
  

  end;  

please somebody helpme