ControlP5 ControlFrame not working P3.1.1

I just upgraded to Processing 3.1.1 and updated the ControlP5 library, and my code that was working earlier on P3 is now throwing an error I can't trace. The error is: The method add(Component) in the type Container is not applicable for the arguements (MyApp.ControlFrame)

Error is thrown on f.add(p); below

    ControlFrame addControlFrame(String theName, int theWidth, int theHeight) {
      PImage icon = loadImage("MY_LOGO.png");
      frame.setIconImage(icon.getImage());    //  ========== SET WINDOW ICON

      Frame f = new Frame(theName);
      ControlFrame p = new ControlFrame(this, theWidth, theHeight);
      f.add(p);
      p.init();
      f.setTitle(theName);
      f.setSize(p.w, p.h);
      f.setLocation(displayWidth - 250, 30);
      f.setResizable(true);
      f.setVisible(true);
      f.setAlwaysOnTop( true );
      f.setIconImage(icon.getImage());    //  ========== SET WINDOW ICON
      return p;
    }

Has something changed in the latest release of Processing to cause this, or am I missing something else? Any suggestions and/or insights are very much welcome.