Comment 5 for bug 657183

Yep. It seems that :DEFAULT doesn't get treated right.

* (sb-impl::default-external-format)

:UTF-8
* (sb-impl::external-format-char-size :default)

1
* (sb-impl::get-external-format :default)

NIL
NIL

However, I think the right place to fix this is making GET-EXTERNAL-FORMAT understand :DEFAULT.