Array of set of enum whose first element is empty

[rtaupe]

It´s great that MiniZinc supports enums, and they work really fine in most of the cases, for example as follows:

enum E = { A, B, C };
array[1..3] of set of E: e;
e = [ {A}, {A,B}, {} ];
solve satisfy;

However, if I specify the first element of an array of sets of enum to be empty, I get an unexpected error:

enum E = { A, B, C };
array[1..3] of set of E: e;
e = [ {}, {A,B}, {} ];
solve satisfy;

MiniZinc: type error: initialisation value for 'e' has invalid type-inst: expected 'array[int] of set of E', actual 'array[int] of set of int'