Countax counting "zero" values

Hello, 

I have bucketed my consumer according to their sales amount using a measure:

It means all my customer are allocated in bucket size.

In order to see how many customer I have behind each bucket I used COUNTAX :

COUNTAX(Customer;[Bucket Size CY])

My problem is : I have some customer that have made sales for "zéro EURO". It means that their is a row with the Name of the customer and on the field "sales " their is "=0"

My Countax take in account those customer with zero sales... 

Is it a way to filter this in the countax formula ?

Thanks