PlayerPrefsX unknown identifier

Not sure if this is a Unity 5 thing, but for some reason, using UnityScript, I’m getting the Unknown identifier error using PlayerPrefsX

var foo = new int[10];
for (i in foo)
   i = Random.Range(1, 100);
PlayerPrefsX.SetIntArray("SomeNumbers", foo);
var bar = PlayerPrefsX.GetIntArray("SomeNumbers");
for (i in bar)
   print (i);

PlayerPrefsX is an old script that was used before playerprefs worked correctly I believe. Where did you come across it?