diff --git a/dev/add-source.sh b/dev/add-source.sh
new file mode 100755
index 0000000..5f62caa
--- /dev/null
+++ b/dev/add-source.sh
@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+_usage="
+A wrapper script around \`npins\` for adding sources to catppuccin/nix
+
+Usage: $(basename "$0") repo_name [branch]
+
+Options:
+
+repo_name           Name of the repository in the Catppuccin org
+branch              Primary branch of the repository (defaults to main if omitted)
+"
+
+repo_name="${1:-}"
+branch_name="${2:-main}"
+
+if [ "${repo_name:-}" = "" ]; then
+    echo "error: a repository name is required!" >&2
+    echo "$_usage"
+    exit 1
+fi
+
+npins add github \
+  catppuccin "$repo_name" \
+  --directory ./.sources \
+  --branch "$branch_name"
diff --git a/dev/add_source.sh b/dev/add_source.sh
deleted file mode 100644
index 7c0bee0..0000000
--- a/dev/add_source.sh
+++ /dev/null
@@ -1,22 +0,0 @@
-#!/usr/bin/env bash
-set -e
-
-_usage="
-Usage: add-source <repo_name> [branch]
-repo_name: Name of the repository in the Catppuccin org (required)
-branch: Primary branch of the repository (optional, defaults to main)
-"
-
-repo_name="${1}"
-branch_name="${2:-main}"
-
-if [ "${repo_name:-}" = "" ]; then
-    echo "error: a repository name is required!" >&2
-    echo "$_usage"
-    exit 1
-fi
-
-npins add github \
-  catppuccin "$repo_name" \
-  --directory ./.sources \
-  --branch "$branch_name"
diff --git a/dev/flake.nix b/dev/flake.nix
index a3eb30d..7dadc9d 100644
--- a/dev/flake.nix
+++ b/dev/flake.nix
@@ -37,34 +37,16 @@
         stable = nixpkgs-stable.legacyPackages.${system};
       });
 
-      forAllSystems = fn: nixpkgs.lib.genAttrs systems (system: fn nixpkgsFor.${system}.unstable);
+      forAllSystems = nixpkgs.lib.genAttrs systems;
     in
     {
       apps = forAllSystems (
+        system:
+        let
+          pkgs = nixpkgsFor.${system}.unstable;
+          inherit (pkgs) lib;
+        in
         {
-          lib,
-          pkgs,
-          system,
-          ...
-        }:
-        {
-          add-source = {
-            type = "app";
-            program = lib.getExe (
-              pkgs.runCommand "add-source"
-                {
-                  nativeBuildInputs = [ pkgs.makeWrapper ];
-                  meta.mainProgram = "add-source";
-                }
-                ''
-                  mkdir -p $out/bin
-                  install -Dm755 ${./add_source.sh} $out/bin/add-source
-                  wrapProgram $out/bin/add-source \
-                    --prefix PATH : ${lib.makeBinPath [ pkgs.npins ]}
-                ''
-            );
-          };
-
           serve = {
             type = "app";
             program = lib.getExe self.packages.${system}.site.serve;
@@ -73,29 +55,23 @@
       );
 
       checks = forAllSystems (
-        {
-          lib,
-          pkgs,
-          system,
-          ...
-        }:
-        import ../tests {
-          inherit lib home-manager home-manager-stable;
-          nixpkgs = pkgs;
+        system:
+        import ../tests rec {
+          inherit home-manager home-manager-stable;
+          inherit (nixpkgs) lib;
+          nixpkgs = nixpkgsFor.${system}.unstable;
           nixpkgs-stable = nixpkgsFor.${system}.stable;
         }
       );
 
-      formatter = forAllSystems (pkgs: pkgs.nixfmt-rfc-style);
+      formatter = forAllSystems (system: nixpkgsFor.${system}.unstable.nixfmt-rfc-style);
 
       packages = forAllSystems (
-        {
-          lib,
-          pkgs,
-          system,
-          ...
-        }:
+        system:
         let
+          pkgs = nixpkgsFor.${system}.unstable;
+          inherit (pkgs) lib;
+
           version = self.shortRev or self.dirtyShortRev or "unknown";
           mkOptionDoc = pkgs.callPackage ../docs/options-doc.nix { };
           mkSite = pkgs.callPackage ../docs/mk-site.nix { };
@@ -131,6 +107,23 @@
             homeManagerDoc = packages'.home-manager-doc;
           };
 
+          add-source =
+            pkgs.runCommand "add-source"
+              {
+                nativeBuildInputs = [ pkgs.patsh ];
+                buildInputs = [ pkgs.npins ];
+                meta.mainProgram = "add-source";
+              }
+              ''
+                mkdir -p $out/bin
+
+                patsh \
+                  --store-dir ${builtins.storeDir} \
+                  ${./add-source.sh} $out/bin/add-source
+
+                chmod 755 $out/bin/add-source
+              '';
+
           default = packages'.site;
         }
       );