diff --git a/.github/workflows/nix.yml b/.github/workflows/nix.yml
index d3f17fb..83bff84 100644
--- a/.github/workflows/nix.yml
+++ b/.github/workflows/nix.yml
@@ -2,18 +2,25 @@ name: "Nix"
 on:
   pull_request:
   push:
+  workflow_dispatch:
 jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
-    - uses: cachix/install-nix-action@v6
-    - uses: cachix/cachix-action@v3
+    - uses: actions/checkout@v2.3.4
+    - uses: cachix/install-nix-action@v13
+      with:
+          install_url: https://github.com/numtide/nix-unstable-installer/releases/download/nix-2.5pre20211015_130284b/install
+          extra_nix_config: |
+            experimental-features = nix-command flakes
+    - uses: cachix/cachix-action@v10
       with:
         name: xe
     - run: |
-        rm result
-        nix-build docker.nix
-        docker load -i result
+        nix build .#docker --impure
+        # the shell expansion will identify the build, and, because we know
+        # we're guaranteed to only have one file in result/docker due to the
+        # pure flake, will always properly expand to just the one target image.
+        docker load -i result/docker/*
         docker run --rm xena/pahi:latest /bin/testrunner
         docker run --rm -w /wasm xena/pahi:latest /tests/bench.sh
diff --git a/default.nix b/default.nix
deleted file mode 100644
index 055efd0..0000000
--- a/default.nix
+++ /dev/null
@@ -1,63 +0,0 @@
-{ sources ? import ./nix/sources.nix }:
-let
-  rust = import ./nix/rust.nix { inherit sources; };
-  pkgs = import sources.nixpkgs { };
-  dhall = import ./nix/dhall.nix { inherit sources pkgs; };
-  olin-cwa = import sources.olin { };
-  naersk = pkgs.callPackage sources.naersk {
-    rustc = rust;
-    cargo = rust;
-  };
-  name = "pahi";
-  src = builtins.filterSource
-    (path: type: type != "directory" || builtins.baseNameOf path != "target")
-    ./.;
-
-  pahi = naersk.buildPackage {
-    inherit name src;
-    buildInputs = [ pkgs.openssl pkgs.pkg-config ];
-  };
-
-  olin = naersk.buildPackage {
-    name = "olin";
-    src = ./wasm;
-
-    buildInputs = [ olin-cwa ];
-    doCheck = false;
-  };
-
-  olin-spec = import ./olin-spec { inherit pkgs sources; };
-  docs = import ./docs { inherit pkgs sources; };
-  pahi-testrunner = import ./tests { inherit pkgs sources; };
-
-  composite = pkgs.stdenv.mkDerivation {
-    version = "latest";
-    phases = "installPhase";
-    inherit name src;
-
-    installPhase = ''
-      mkdir -p $out/docs/olin-spec
-      cp -rf ${docs}/docs $out
-      cp -rf ${olin-spec}/docs $out
-      mkdir -p $out/bin
-      cp -rf ${olin-cwa}/bin/cwa $out/bin
-      cp -rf ${pahi}/bin/pahi $out/bin
-      mkdir -p $out/wasm
-
-      for f in ${olin}/bin/*
-      do
-        cp "$f" "$out/wasm/$(basename $f)".wasm
-      done
-
-      cp -rf ${olin-cwa}/wasm/zig $out/wasm/zig
-
-      cp -rf ${pahi-testrunner}/bin/tests $out/bin/testrunner
-      mkdir -p $out/tests
-      cp -rf ${pahi-testrunner}/tests/testdata.dhall $out/tests/testdata.dhall
-      cp -rf ${pahi-testrunner}/tests/bench.sh $out/tests/bench.sh
-
-      cp $src/README.md $out/README.md
-      cp $src/LICENSE $out/LICENSE
-    '';
-  };
-in composite
diff --git a/docker.nix b/docker.nix
deleted file mode 100644
index 847c865..0000000
--- a/docker.nix
+++ /dev/null
@@ -1,31 +0,0 @@
-{ system ? builtins.currentSystem }:
-
-let
-  sources = import ./nix/sources.nix;
-  pkgs = import sources.nixpkgs { };
-  dhall = import ./nix/dhall.nix;
-  callPackage = pkgs.lib.callPackageWith pkgs;
-  pahi = callPackage ./default.nix { };
-
-  dockerImage = pkg:
-    pkgs.dockerTools.buildLayeredImage {
-      name = "xena/pahi";
-      tag = "latest";
-
-      contents = [
-        pkg
-        pkgs.bash
-        pkgs.cacert
-        pkgs.coreutils
-        pkgs.hyperfine
-        dhall.dhall-json-simple
-      ];
-
-      config = {
-        Cmd = [ "/bin/bash" ];
-        WorkingDir = "/";
-        Env = [ "NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt" ];
-      };
-    };
-
-in dockerImage pahi
diff --git a/docs/default.nix b/docs/default.nix
index 5445160..136eaf8 100644
--- a/docs/default.nix
+++ b/docs/default.nix
@@ -1,4 +1,4 @@
-{ sources ? import ../nix/sources.nix, pkgs ? import sources.nixpkgs { }}:
+{ pkgs }:
 let
   src = builtins.filterSource
     (path: type: type != "directory" || builtins.baseNameOf path != "olin-spec")
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..292b153
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,115 @@
+{
+  "nodes": {
+    "dhall-lang": {
+      "flake": false,
+      "locked": {
+        "narHash": "sha256-4CHI3du+DpCeU6vdsirhyuvJXt/9Rl89EkdB//SKHKM=",
+        "type": "tarball",
+        "url": "https://github.com/dhall-lang/dhall-lang/archive/ccb9f5d54b0ecba05a6493e84442ce445e411e9e.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://github.com/dhall-lang/dhall-lang/archive/ccb9f5d54b0ecba05a6493e84442ce445e411e9e.tar.gz"
+      }
+    },
+    "easy-dhall-nix": {
+      "flake": false,
+      "locked": {
+        "narHash": "sha256-r6cU2A2yqRzNkp000TdR5bTCIQGLvfOxiGh5uHjwGQ8=",
+        "type": "tarball",
+        "url": "https://github.com/justinwoo/easy-dhall-nix/archive/7c22a145fcb8e00b61d29efc7543af0c80d709ed.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://github.com/justinwoo/easy-dhall-nix/archive/7c22a145fcb8e00b61d29efc7543af0c80d709ed.tar.gz"
+      }
+    },
+    "naersk": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      },
+      "locked": {
+        "lastModified": 1632266297,
+        "narHash": "sha256-J1yeJk6Gud9ef2pEf6aKQemrfg1pVngYDSh+SAY94xk=",
+        "owner": "nix-community",
+        "repo": "naersk",
+        "rev": "ee7edec50b49ab6d69b06d62f1de554efccb1ccd",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "naersk",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1634073448,
+        "narHash": "sha256-e0z1FxOf6BrPUmzgUKlCLf+jA9aHAOT0pLFctHQveGo=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "5b5d681a0724cc351e84950e6ec92b22134c0e1a",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "nixpkgs-mozilla": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1629225446,
+        "narHash": "sha256-HJX4Pc5ZUAg4apxB/XHuJ+6ukzvRQqeZMjscOBst2bA=",
+        "owner": "mozilla",
+        "repo": "nixpkgs-mozilla",
+        "rev": "0510159186dd2ef46e5464484fbdf119393afa58",
+        "type": "github"
+      },
+      "original": {
+        "owner": "mozilla",
+        "repo": "nixpkgs-mozilla",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1634073448,
+        "narHash": "sha256-e0z1FxOf6BrPUmzgUKlCLf+jA9aHAOT0pLFctHQveGo=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "5b5d681a0724cc351e84950e6ec92b22134c0e1a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "olin": {
+      "flake": false,
+      "locked": {
+        "narHash": "sha256-r8valcDgcyd9LiiW5I0spUTf4TbTycya2W1eQgjt0ZE=",
+        "type": "tarball",
+        "url": "https://github.com/Xe/olin/archive/0e8c8eea725307f8f396919cbf7f965a0d67b0e0.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://github.com/Xe/olin/archive/0e8c8eea725307f8f396919cbf7f965a0d67b0e0.tar.gz"
+      }
+    },
+    "root": {
+      "inputs": {
+        "dhall-lang": "dhall-lang",
+        "easy-dhall-nix": "easy-dhall-nix",
+        "naersk": "naersk",
+        "nixpkgs": "nixpkgs_2",
+        "nixpkgs-mozilla": "nixpkgs-mozilla",
+        "olin": "olin"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..c62d559
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,153 @@
+{
+  description = "The next-generation Olin runtime, made with love";
+
+  inputs.dhall-lang.url = "https://github.com/dhall-lang/dhall-lang/archive/ccb9f5d54b0ecba05a6493e84442ce445e411e9e.tar.gz";
+  inputs.dhall-lang.flake = false;
+
+  inputs.easy-dhall-nix.url = "https://github.com/justinwoo/easy-dhall-nix/archive/7c22a145fcb8e00b61d29efc7543af0c80d709ed.tar.gz";
+  inputs.easy-dhall-nix.flake = false;
+
+  inputs.naersk.url = "github:nix-community/naersk";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs";
+
+  inputs.nixpkgs-mozilla.url = "github:mozilla/nixpkgs-mozilla";
+  inputs.nixpkgs-mozilla.flake = false;
+
+  inputs.olin.url = "https://github.com/Xe/olin/archive/0e8c8eea725307f8f396919cbf7f965a0d67b0e0.tar.gz";
+  inputs.olin.flake = false;
+
+  outputs = { self, dhall-lang, easy-dhall-nix, naersk, nixpkgs, nixpkgs-mozilla, olin }:
+    let
+      pkgs = import nixpkgs { system = "x86_64-linux"; };
+      naersk-lib = naersk.lib."x86_64-linux".override { rustc = rust; };
+
+      mozilla = pkgs.callPackage (nixpkgs-mozilla + "/package-set.nix") {};
+      rust = let
+          channel = "nightly";
+          date = "2020-07-27";
+          targets = [ "wasm32-unknown-unknown" "wasm32-wasi" ];
+        in (mozilla.rustChannelOf {
+          inherit channel date;
+          sha256 = "sha256-75eK1CNDEkeVvJ1phWOHZBuujMhalYCxbi5sgAFUlvI=";
+        }).rust.override { inherit targets; };
+
+      dhall = import easy-dhall-nix { inherit pkgs; };
+      dhall-lang-pkg = import dhall-lang { inherit pkgs; };
+      olin-cwa = import olin { inherit pkgs; };
+
+      olin-spec = import ./olin-spec {
+        inherit dhall-lang pkgs;
+        dhall = import easy-dhall-nix { inherit pkgs; };
+      };
+
+      docs = import ./docs { inherit pkgs; };
+      pahi-testrunner = import ./tests { inherit pkgs; };
+
+      olin-pkg = naersk-lib.buildPackage {
+        name = "olin";
+        src = ./wasm;
+
+        buildInputs = [ olin-cwa ];
+        doCheck = false;
+      };
+
+      pahi = naersk-lib.buildPackage {
+        inherit name src;
+        buildInputs = [ pkgs.openssl pkgs.pkg-config ];
+      };
+
+      name = "pahi";
+      src = builtins.filterSource
+        (path: type: type != "directory" || builtins.baseNameOf path != "target")
+        ./.;
+
+    in {
+      defaultPackage.x86_64-linux = pkgs.stdenv.mkDerivation {
+        version = "latest";
+        phases = "buildPhase installPhase";
+        inherit name src;
+
+        installPhase = ''
+          mkdir -p $out/docs/olin-spec
+          cp -rf ${docs}/docs $out
+          cp -rf ${olin-spec}/docs $out
+          mkdir -p $out/bin
+          cp -rf ${olin-cwa}/bin/cwa $out/bin
+          cp -rf ${pahi}/bin/pahi $out/bin
+          mkdir -p $out/wasm
+
+          for f in ${olin-pkg}/bin/*
+          do
+<<<<<<< HEAD
+            cp "$f" "$out/wasm/$(basename $f)"
+=======
+            cp "$f" "$out/wasm/$(basename $f)".wasm
+>>>>>>> main
+          done
+
+          cp -rf ${olin-cwa}/wasm/zig $out/wasm/zig
+
+          cp -rf ${pahi-testrunner}/bin/tests $out/bin/testrunner
+          mkdir -p $out/tests
+          cp -rf ${pahi-testrunner}/tests/testdata.dhall $out/tests/testdata.dhall
+          cp -rf ${pahi-testrunner}/tests/bench.sh $out/tests/bench.sh
+
+          cp $src/README.md $out/README.md
+          cp $src/LICENSE $out/LICENSE
+        '';
+      };
+
+<<<<<<< HEAD
+=======
+      devShell.x86_64-linux = pkgs.mkShell {
+        buildInputs = [
+          rust
+
+          pkgs.hyperfine
+
+          pkgs.openssl
+          pkgs.pkg-config
+
+          dhall-lang-pkg
+          dhall
+
+          pkgs.go
+          olin
+        ];
+      };
+
+>>>>>>> main
+      packages.x86_64-linux.docker = let
+        img = pkgs.dockerTools.buildLayeredImage {
+          name = "xena/pahi";
+          tag = "latest";
+
+          contents = [ self.defaultPackage.x86_64-linux # pahi
+                       pkgs.bash pkgs.coreutils pkgs.cacert pkgs.hyperfine
+<<<<<<< HEAD
+                       dhall.dhall-json-simple dhall-lang ];
+=======
+                       dhall.dhall-json-simple ];
+>>>>>>> main
+
+          config = {
+            Cmd = [ "/bin/bash" ];
+            WorkingDir = "/";
+            Env = [ "NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt" ];
+          };
+        };
+      in pkgs.stdenv.mkDerivation {
+        name = "pahi-docker";
+        version = "latest";
+        src = ./.; # this is a bit of a lie, but it works
+
+        installPhase = ''
+          mkdir -p $out/docker/
+          cp ${img} $out/docker/
+        '';
+
+        doConfigure = false;
+        doBuild = false;
+      };
+    };
+}
diff --git a/nix/dhall.nix b/nix/dhall.nix
deleted file mode 100644
index 2e12e25..0000000
--- a/nix/dhall.nix
+++ /dev/null
@@ -1,5 +0,0 @@
-let
-  sources = import ./sources.nix;
-  pkgs = import sources.nixpkgs { };
-  dhall = import sources.easy-dhall-nix { inherit pkgs; };
-in dhall
diff --git a/nix/rust.nix b/nix/rust.nix
deleted file mode 100644
index 3b7f8ad..0000000
--- a/nix/rust.nix
+++ /dev/null
@@ -1,9 +0,0 @@
-{ sources ? import ./sources.nix }:
-
-let
-  pkgs =
-    import sources.nixpkgs { overlays = [ (import sources.nixpkgs-mozilla) ]; };
-  channel = "nightly";
-  date = "2020-07-27";
-  targets = [ "wasm32-unknown-unknown" "wasm32-wasi" ];
-in pkgs.rustChannelOfTargets channel date targets
diff --git a/nix/sources.json b/nix/sources.json
deleted file mode 100644
index cb81160..0000000
--- a/nix/sources.json
+++ /dev/null
@@ -1,86 +0,0 @@
-{
-    "dhall-lang": {
-        "branch": "master",
-        "description": "Maintainable configuration files",
-        "homepage": "https://dhall-lang.org",
-        "owner": "dhall-lang",
-        "repo": "dhall-lang",
-        "rev": "ccb9f5d54b0ecba05a6493e84442ce445e411e9e",
-        "sha256": "18qwibsgyha728ymyipxvxgcksyaw4mb5pdbafg903myvgfwh8g0",
-        "type": "tarball",
-        "url": "https://github.com/dhall-lang/dhall-lang/archive/ccb9f5d54b0ecba05a6493e84442ce445e411e9e.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "easy-dhall-nix": {
-        "branch": "master",
-        "description": "Derivations for easily downloading Dhall binaries and putting them to use.",
-        "homepage": "",
-        "owner": "justinwoo",
-        "repo": "easy-dhall-nix",
-        "rev": "7c22a145fcb8e00b61d29efc7543af0c80d709ed",
-        "sha256": "03qry1wbhyb8i2qz7gcb04hw5d75a4vx2d4xjb6iradj1pc199xg",
-        "type": "tarball",
-        "url": "https://github.com/justinwoo/easy-dhall-nix/archive/7c22a145fcb8e00b61d29efc7543af0c80d709ed.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "naersk": {
-        "branch": "master",
-        "description": "Build rust crates in Nix. No configuration, no code generation. IFD and sandbox friendly.",
-        "homepage": "",
-        "owner": "nmattia",
-        "repo": "naersk",
-        "rev": "dcee40445cfe301ced2d1b11290d6a94ff3aadb9",
-        "sha256": "0n9d1zirrhi9cr31kbxifrxkk52grbny04xnn1qhmvskyc11pcm4",
-        "type": "tarball",
-        "url": "https://github.com/nmattia/naersk/archive/dcee40445cfe301ced2d1b11290d6a94ff3aadb9.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "niv": {
-        "branch": "master",
-        "description": "Easy dependency management for Nix projects",
-        "homepage": "https://github.com/nmattia/niv",
-        "owner": "nmattia",
-        "repo": "niv",
-        "rev": "ab9cc41caf44d1f1d465d8028e4bc0096fd73238",
-        "sha256": "17k52n8zwp832cqifsc4458mhy4044wmk22f807171hf6p7l4xvr",
-        "type": "tarball",
-        "url": "https://github.com/nmattia/niv/archive/ab9cc41caf44d1f1d465d8028e4bc0096fd73238.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "nixpkgs": {
-        "branch": "nixpkgs-unstable",
-        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
-        "homepage": "https://github.com/NixOS/nixpkgs",
-        "owner": "NixOS",
-        "repo": "nixpkgs-channels",
-        "rev": "5ad1cdafe15d4ea79ae6abcddc360dd2de35b44e",
-        "sha256": "1nn602v3ssj79rxdfl3ical10c1d632vji9nv2h0dqslmycg4aws",
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs-channels/archive/5ad1cdafe15d4ea79ae6abcddc360dd2de35b44e.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "nixpkgs-mozilla": {
-        "branch": "master",
-        "description": "mozilla related nixpkgs (extends nixos/nixpkgs repo)",
-        "homepage": null,
-        "owner": "mozilla",
-        "repo": "nixpkgs-mozilla",
-        "rev": "efda5b357451dbb0431f983cca679ae3cd9b9829",
-        "sha256": "11wqrg86g3qva67vnk81ynvqyfj0zxk83cbrf0p9hsvxiwxs8469",
-        "type": "tarball",
-        "url": "https://github.com/mozilla/nixpkgs-mozilla/archive/efda5b357451dbb0431f983cca679ae3cd9b9829.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "olin": {
-        "branch": "master",
-        "description": "Webassembly + Event Sourcing",
-        "homepage": "",
-        "owner": "Xe",
-        "repo": "olin",
-        "rev": "0e8c8eea725307f8f396919cbf7f965a0d67b0e0",
-        "sha256": "14fixl444pkdv6dcrjfk6vhxyi555j6y95i85ryjfwz0q2axmjxg",
-        "type": "tarball",
-        "url": "https://github.com/Xe/olin/archive/0e8c8eea725307f8f396919cbf7f965a0d67b0e0.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    }
-}
diff --git a/nix/sources.nix b/nix/sources.nix
deleted file mode 100644
index 8a725cb..0000000
--- a/nix/sources.nix
+++ /dev/null
@@ -1,134 +0,0 @@
-# This file has been generated by Niv.
-
-let
-
-  #
-  # The fetchers. fetch_<type> fetches specs of type <type>.
-  #
-
-  fetch_file = pkgs: spec:
-    if spec.builtin or true then
-      builtins_fetchurl { inherit (spec) url sha256; }
-    else
-      pkgs.fetchurl { inherit (spec) url sha256; };
-
-  fetch_tarball = pkgs: spec:
-    if spec.builtin or true then
-      builtins_fetchTarball { inherit (spec) url sha256; }
-    else
-      pkgs.fetchzip { inherit (spec) url sha256; };
-
-  fetch_git = spec:
-    builtins.fetchGit { url = spec.repo; inherit (spec) rev ref; };
-
-  fetch_builtin-tarball = spec:
-    builtins.trace
-      ''
-        WARNING:
-          The niv type "builtin-tarball" will soon be deprecated. You should
-          instead use `builtin = true`.
-
-          $ niv modify <package> -a type=tarball -a builtin=true
-      ''
-      builtins_fetchTarball { inherit (spec) url sha256; };
-
-  fetch_builtin-url = spec:
-    builtins.trace
-      ''
-        WARNING:
-          The niv type "builtin-url" will soon be deprecated. You should
-          instead use `builtin = true`.
-
-          $ niv modify <package> -a type=file -a builtin=true
-      ''
-      (builtins_fetchurl { inherit (spec) url sha256; });
-
-  #
-  # Various helpers
-  #
-
-  # The set of packages used when specs are fetched using non-builtins.
-  mkPkgs = sources:
-    let
-      sourcesNixpkgs =
-        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) {};
-      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
-      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
-    in
-      if builtins.hasAttr "nixpkgs" sources
-      then sourcesNixpkgs
-      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
-        import <nixpkgs> {}
-      else
-        abort
-          ''
-            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
-            add a package called "nixpkgs" to your sources.json.
-          '';
-
-  # The actual fetching function.
-  fetch = pkgs: name: spec:
-
-    if ! builtins.hasAttr "type" spec then
-      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
-    else if spec.type == "file" then fetch_file pkgs spec
-    else if spec.type == "tarball" then fetch_tarball pkgs spec
-    else if spec.type == "git" then fetch_git spec
-    else if spec.type == "builtin-tarball" then fetch_builtin-tarball spec
-    else if spec.type == "builtin-url" then fetch_builtin-url spec
-    else
-      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
-
-  # Ports of functions for older nix versions
-
-  # a Nix version of mapAttrs if the built-in doesn't exist
-  mapAttrs = builtins.mapAttrs or (
-    f: set: with builtins;
-    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
-  );
-
-  # fetchTarball version that is compatible between all the versions of Nix
-  builtins_fetchTarball = { url, sha256 }@attrs:
-    let
-      inherit (builtins) lessThan nixVersion fetchTarball;
-    in
-      if lessThan nixVersion "1.12" then
-        fetchTarball { inherit url; }
-      else
-        fetchTarball attrs;
-
-  # fetchurl version that is compatible between all the versions of Nix
-  builtins_fetchurl = { url, sha256 }@attrs:
-    let
-      inherit (builtins) lessThan nixVersion fetchurl;
-    in
-      if lessThan nixVersion "1.12" then
-        fetchurl { inherit url; }
-      else
-        fetchurl attrs;
-
-  # Create the final "sources" from the config
-  mkSources = config:
-    mapAttrs (
-      name: spec:
-        if builtins.hasAttr "outPath" spec
-        then abort
-          "The values in sources.json should not have an 'outPath' attribute"
-        else
-          spec // { outPath = fetch config.pkgs name spec; }
-    ) config.sources;
-
-  # The "config" used by the fetchers
-  mkConfig =
-    { sourcesFile ? ./sources.json
-    , sources ? builtins.fromJSON (builtins.readFile sourcesFile)
-    , pkgs ? mkPkgs sources
-    }: rec {
-      # The sources, i.e. the attribute set of spec name to spec
-      inherit sources;
-
-      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
-      inherit pkgs;
-    };
-in
-mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }
diff --git a/olin-spec/default.nix b/olin-spec/default.nix
index 62beeaa..515c9fc 100644
--- a/olin-spec/default.nix
+++ b/olin-spec/default.nix
@@ -1,5 +1,4 @@
-{ sources ? import ../nix/sources.nix, pkgs ? import sources.nixpkgs { }
-, dhall-lang ? sources.dhall-lang, dhall ? import ../nix/dhall.nix }:
+{ pkgs, dhall-lang, dhall }:
 pkgs.stdenv.mkDerivation rec {
   name = "olin-spec";
   version = "latest";
diff --git a/shell.nix b/shell.nix
deleted file mode 100644
index d0f54aa..0000000
--- a/shell.nix
+++ /dev/null
@@ -1,35 +0,0 @@
-let
-  sources = import ./nix/sources.nix;
-  niv = import sources.niv { };
-  pkgs = import sources.nixpkgs { };
-  olin = import sources.olin { inherit pkgs; };
-  rust = import ./nix/rust.nix { inherit sources; };
-  dhall = import ./nix/dhall.nix;
-in pkgs.mkShell {
-  buildInputs = [
-    rust
-
-    # benchmarks
-    pkgs.hyperfine
-
-    # dependency management
-    niv.niv
-
-    # native dependencies
-    pkgs.openssl
-    pkgs.pkg-config
-
-    # olin-docs
-    dhall.dhall-simple
-    sources.dhall-lang
-
-    # tests
-    pkgs.go
-    olin
-  ];
-  nativeBuildInputs = [ pkgs.removeReferencesTo ];
-
-  # envvars
-  RUST_LOG = "pahi=error,pahi_olin=debug";
-  MAGIC_CONCH = "yes";
-}
diff --git a/tests/default.nix b/tests/default.nix
index 0927752..c0e3aad 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -1,4 +1,4 @@
-{ sources ? import ../nix/sources.nix, pkgs ? import sources.nixpkgs { } }:
+{ pkgs  }:
 with pkgs;
 buildGoPackage {
   name = "pahi-tests";