import (fetchTarball {
    url = "https://github.com/NixOS/nixpkgs-channels/archive/696c6bed4e8e2d9fd9b956dea7e5d49531e9d13f.tar.gz";
    # Wait till new nix version is released.
    #sha256 = "1b4h12y45h08c7dxa6420qmspv6k82p3sw4xzz8g53k7s7dg128z";
  }
)