DAX Rolling 12 month with no value in a month

[Coline]

Hi,

I'm blocked on my Sum Rolling 12 months measure:

When I want to split by category, it's possible to have no value in the last month that I want to begin the 12 months, in this case, the Rolling 12 months doesn't sum with the previous 11 months.

In this example, line 5, I have nothing, or I have to have 4. It's because I want the rolling for November, and in november I have no value for line 5.

My measure:

A 12MG = CALCULATE([A];

          DATESINPERIOD('Date'[Date];

                       LASTDATE('Date'[Date]);-12;MONTH))

Can someone help me?

Thanks