e generation question

Hi,

the next code used to work in IES 13.2 but results in error in 14.2.

var idx : uint[0..7];
var num : byte = 0xA;
gen idx keeping {read_only(num[it:it] == 0);};

I am getting the next error message:

GEN_NO_GENERATABLE_NOTIF

Why ?

How should I rewirte this to do the same functionality, without converting the var num into a list ?

Thanks.