Field Parameter and sorting

Hi,

I have this field parameter

I have this Field Parameter

FP_YearMonth = {

    ("Year", NAMEOF('Calendar'[Year]), 0),

    ("Month Year", NAMEOF('Calendar'[Month Year]), 1)

}

Month Year are values like 'Dec-2018, Jan-2019'

I use this in a visual. When I choose Month-Year it gives the data in ascending order, because Mont-Year is sorted by column Year-Month (201812, 201901 etc) 

When I click on Year, it constantly makes a mess on the sorting order

How can I fix this?

Regards
Ron