PlayerPrefsX Question

This has been a huge help thus far, but I've become stuck with a bit of syntax in the storing arrays function. I get an error saying "No appropriate version of 'PlayerPrefsX.SetStringArray' for the argument list '(String, Array)' was found. I'm not sure where my problem is. directionArray is the array I want to save:

    // Store directionArray in a file
    if (!PlayerPrefsX.SetStringArray("directionArrayPerm_1", directionArray))
Debug.Log("Oops, directionArray saving failed");