# subgroup of number field unit group

I would like to be able to create subgroups of a unit group generated by given elements. I haven't, thus far, been able to find a way to make this work. The following doesn't work:

```
N.<a> = NumberField(x^3+2)
G = N.unit_group()
g = G.random_element()
G.subgroup([g])
```

Can anyone help me find a workaround?

(Note: it appears to be a bug, see trac.sagemath.org/ticket/18863, but I'm just looking for a workaround for now.)