+with import (builtins.fetchTarball {
+ # FIXME: upgrade to nixpkgs 19 when stable and stick to stable
+ # versions
+ name = "nixos-unstable-2018-12-08";
+ url = https://github.com/nixos/nixpkgs/archive/61c3169a0e17d789c566d5b241bfe309ce4a6275.tar.gz;
+ sha256 = "0qbycg7wkb71v20rchlkafrjfpbk2fnlvvbh3ai9pyfisci5wxvq";
+}) {};