Oh, good to leave as is, then! Thanks. "will install the default" seems optimistic:
```
# apt-get install zeroc-ice
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package zeroc-ice is a virtual package provided by:
  zeroc-ice35 3.5.1-5.1
  zeroc-ice34 3.4.2-8.2
You should explicitly select one to install.

E: Package 'zeroc-ice' has no installation candidate
```
but maybe my configuration is strange and it still tells me what I may choose, which suffices.