-with (import <nixpkgs> {}).pkgs;
-let hspkgs = haskell-ng.packages.ghc7101.override {
+{ pkgs ? import <nixpkgs> {}, compiler ? "ghc7101" }:
+let hspkgs = pkgs.haskell.packages.${compiler}.override {
overrides = self: super: {
hmacaroons = self.callPackage ./. {};
};