diff --git a/default.nix b/default.nix
index 74164e1..e72dd52 100644
--- a/default.nix
+++ b/default.nix
@@ -145,6 +145,7 @@ with rec
   # version from `package.yaml` and create a dummy module that we inject in the
   # `ghci` command.
   niv-devshell = haskellPackages.shellFor {
+    buildInputs = [ pkgs.nixpkgs-fmt ];
     packages = ps: [ ps.niv ];
     shellHook = ''
       repl_for() {
diff --git a/nix/default.nix b/nix/default.nix
index 144718e..a4d3eee 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -2,6 +2,7 @@
 import sources.nixpkgs {
   overlays = [
     (_: pkgs: { inherit sources; })
+    (_: pkgs: { nixpkgs-fmt = import pkgs.sources.nixpkgs-fmt {}; })
     (_: pkgs: { termtosvg = pkgs.callPackage ./termtosvg.nix {}; })
   ];
   config = {};
diff --git a/nix/sources.json b/nix/sources.json
index a4b32f6..4204651 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -11,6 +11,18 @@
         "url": "https://github.com/NixOS/nixpkgs-channels/archive/d85e435b7bded2596d7b201bcd938c94d8a921c1.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
+    "nixpkgs-fmt": {
+        "branch": "master",
+        "description": "Nix code formatter for nixpkgs [maintainer=@zimbatm]",
+        "homepage": "https://nix-community.github.io/nixpkgs-fmt/",
+        "owner": "nix-community",
+        "repo": "nixpkgs-fmt",
+        "rev": "2a64f4b6a597d0d62004ffcec3ae4fd83cd1efc8",
+        "sha256": "01kx4y1d4c5fjvpcffk92pk9hdbgg5j9h2ryqy2hfm54s7mb0k63",
+        "type": "tarball",
+        "url": "https://github.com/nix-community/nixpkgs-fmt/archive/2a64f4b6a597d0d62004ffcec3ae4fd83cd1efc8.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
     "termtosvg": {
         "branch": "develop",
         "description": "Record terminal sessions as SVG animations",
diff --git a/nix/sources.nix b/nix/sources.nix
index 718ea6f..b53359f 100644
--- a/nix/sources.nix
+++ b/nix/sources.nix
@@ -19,7 +19,7 @@ let
       pkgs.fetchzip { inherit (spec) url sha256; };
 
   fetch_git = spec:
-      builtins.fetchGit { url = spec.repo; inherit (spec) rev ref; };
+    builtins.fetchGit { url = spec.repo; inherit (spec) rev ref; };
 
   fetch_builtin-tarball = spec:
     builtins.trace
@@ -132,5 +132,4 @@ let
       pkgs = mkPkgs sources;
     };
 in
-mkSources (mkConfig {}) //
-  { __functor = _: settings: mkSources (mkConfig settings); }
+mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }
diff --git a/script/test b/script/test
index cc623aa..381f293 100755
--- a/script/test
+++ b/script/test
@@ -2,6 +2,7 @@
 #!nix-shell -i bash
 #!nix-shell -I nixpkgs=./nix
 #!nix-shell -p nix
+#!nix-shell -p nixpkgs-fmt
 #!nix-shell --pure
 
 unset NIX_SSL_CERT_FILE
@@ -32,4 +33,11 @@ fi
 # Build and create a root
 nix-build ${nixargs[@]}
 
+echo "Formatting"
+if ! nixpkgs-fmt --check . ; then
+  echo
+  echo 'run `nixpkgs-fmt .` to fix this issue'
+  exit 1
+fi
+
 echo "all good"
diff --git a/src/Niv/Sources.hs b/src/Niv/Sources.hs
index 0180570..2c9ec14 100644
--- a/src/Niv/Sources.hs
+++ b/src/Niv/Sources.hs
@@ -144,6 +144,7 @@ data SourcesNixVersion
   | V11
   | V12
   | V13
+  | V14
   deriving stock (Bounded, Enum, Eq)
 
 -- | A user friendly version
@@ -162,6 +163,7 @@ sourcesVersionToText = \case
     V11 -> "11"
     V12 -> "12"
     V13 -> "13"
+    V14 -> "14"
 
 latestVersionMD5 :: T.Text
 latestVersionMD5 = sourcesVersionToMD5 maxBound
@@ -187,6 +189,7 @@ sourcesVersionToMD5 = \case
     V11 -> "8a95b7d93b16f7c7515d98f49b0ec741"
     V12 -> "2f9629ad9a8f181ed71d2a59b454970c"
     V13 -> "5e23c56b92eaade4e664cb16dcac1e0a"
+    V14 -> "b470e235e7bcbf106d243fea90b6cfc9"
 
 -- | The MD5 sum of ./nix/sources.nix
 sourcesNixMD5 :: IO T.Text
diff --git a/tests/git/default.nix b/tests/git/default.nix
index b1dc07f..907dd31 100644
--- a/tests/git/default.nix
+++ b/tests/git/default.nix
@@ -6,76 +6,72 @@ pkgs.runCommand "git-test"
   { nativeBuildInputs = [ pkgs.git niv pkgs.nix pkgs.jq ]; }
   (
 
-  # make sure the tests run smoothly in multi-user install
-  # https://github.com/NixOS/nix/issues/3258
-  ''
-    export NIX_STATE_DIR=$TMPDIR
-    export NIX_LOG_DIR=$TMPDIR
-    export HOME=$TMPDIR
-  '' +
-  # First we create a dummy git repo with one commit on master, and one commit
-  # on "branch".
-  ''
-    gitdir=$(mktemp -d)
-    pushd $gitdir > /dev/null
-    git init .
-    echo hello > file
-    git config user.email "niv@foo.bar"
-    git config user.name "Niv Niverson"
-    git add file
-    git commit -m "Initial commit"
-    gitrev=$(git rev-parse HEAD)
+    # make sure the tests run smoothly in multi-user install
+    # https://github.com/NixOS/nix/issues/3258
+    ''
+      export NIX_STATE_DIR=$TMPDIR
+      export NIX_LOG_DIR=$TMPDIR
+      export HOME=$TMPDIR
+    '' + # First we create a dummy git repo with one commit on master, and one commit
+    # on "branch".
+    ''
+      gitdir=$(mktemp -d)
+      pushd $gitdir > /dev/null
+      git init .
+      echo hello > file
+      git config user.email "niv@foo.bar"
+      git config user.name "Niv Niverson"
+      git add file
+      git commit -m "Initial commit"
+      gitrev=$(git rev-parse HEAD)
 
-    git checkout -b branch
-    echo world >> file
-    git add file
-    git commit -m "second commit"
-    gitrev2=$(git rev-parse HEAD)
+      git checkout -b branch
+      echo world >> file
+      git add file
+      git commit -m "second commit"
+      gitrev2=$(git rev-parse HEAD)
 
-    # reset to master as "default branch"
-    git checkout master
-    popd > /dev/null
-  '' +
+      # reset to master as "default branch"
+      git checkout master
+      popd > /dev/null
+    '' + # Then we `niv add` that repo and check some properties, like the revision
+    # and revCount, to make sure it was imported properly, and that sources.nix
+    # does what it's supposed to do.
+    ''
+      nivdir=$(mktemp -d)
+      pushd $nivdir > /dev/null
+      mkdir -p nix
+      echo "{}" > nix/sources.json
+      niv init
+      niv add git -n my-git-repo --repo file://$gitdir
+      nivrev=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.rev' | jq -r)
+      if [ ! "$gitrev" = "$nivrev" ]; then
+        echo "Mismatched revs: $gitrev != $nivrev"
+        exit 42
+      fi
 
-  # Then we `niv add` that repo and check some properties, like the revision
-  # and revCount, to make sure it was imported properly, and that sources.nix
-  # does what it's supposed to do.
-  ''
-    nivdir=$(mktemp -d)
-    pushd $nivdir > /dev/null
-    mkdir -p nix
-    echo "{}" > nix/sources.json
-    niv init
-    niv add git -n my-git-repo --repo file://$gitdir
-    nivrev=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.rev' | jq -r)
-    if [ ! "$gitrev" = "$nivrev" ]; then
-      echo "Mismatched revs: $gitrev != $nivrev"
-      exit 42
-    fi
+      # here we cheat a bit and use "outPath", which actually is the result of
+      # builtins.fetchGit.
+      nivnixrev=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.outPath.rev' | jq -r)
+      if [ ! "$gitrev" = "$nivnixrev" ]; then
+        echo "Mismatched revs: $gitrev != $nivnixrev"
+        exit 42
+      fi
+      nivnixrevcount=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.outPath.revCount')
+      if [ ! "1" -eq "$nivnixrevcount" ]; then
+        echo "Mismatched revCount: 1 != $nivnixrevcount"
+        exit 42
+      fi
 
-    # here we cheat a bit and use "outPath", which actually is the result of
-    # builtins.fetchGit.
-    nivnixrev=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.outPath.rev' | jq -r)
-    if [ ! "$gitrev" = "$nivnixrev" ]; then
-      echo "Mismatched revs: $gitrev != $nivnixrev"
-      exit 42
-    fi
-    nivnixrevcount=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.outPath.revCount')
-    if [ ! "1" -eq "$nivnixrevcount" ]; then
-      echo "Mismatched revCount: 1 != $nivnixrevcount"
-      exit 42
-    fi
+      niv update my-git-repo -a ref=branch
+      nivrev2=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.rev' | jq -r)
+      if [ ! "$gitrev2" = "$nivrev2" ]; then
+        echo "Mismatched revs: $gitrev2 != $nivrev2"
+        exit 42
+      fi
 
-    niv update my-git-repo -a ref=branch
-    nivrev2=$(nix eval --json '(import ./nix/sources.nix).my-git-repo.rev' | jq -r)
-    if [ ! "$gitrev2" = "$nivrev2" ]; then
-      echo "Mismatched revs: $gitrev2 != $nivrev2"
-      exit 42
-    fi
+      popd > /dev/null
 
-    popd > /dev/null
-
-    touch $out
-  ''
+      touch $out
+    ''
   )
-