I'm studying Io and I tried add a value in a list, maybe by the wrong way, but I received a Segmentation fault.

Io> a := list(1, 2, 3, 4)
==> list(1, 2, 3, 4)
Io> a at(0)
==> 1
Io> a at(0) = 1
Segmentation fault (core dumped)