PlayerPrefs.DeleteAll not working

I have this code:

GUILayout.BeginArea (Rect(ScreenX, ScreenY+35, areaWidth, areaHeight));

    if(GUILayout.Button ("Start New Game"))
        {
        PlayerPrefs.DeleteAll;
        Application.LoadLevel("01 - Latest Version 3");
        }

GUILayout.EndArea();

The error I'm getting is:

Expressions in statements must only be executed for their side-effects.

It's a function. You use a function like so:

PlayerPrefs.DeleteAll();