diff --git a/flake.nix b/flake.nix
index 31efafc..eb41e49 100644
--- a/flake.nix
+++ b/flake.nix
@@ -34,17 +34,6 @@
             yj
           ]
           ++ old.buildInputs;
-
-        shellHook =
-          ''
-            # Update package.json
-            if [ -e ./package.json ]; then
-                unlink ./package.json
-            fi
-
-            cat ./package.yaml | yj > ./package.json
-          ''
-          + old.shellHook;
       });
 
       server = nixpkgs.legacyPackages.${system}.mkShell {
diff --git a/templates/.envrc b/templates/.envrc
new file mode 100644
index 0000000..6dc0224
--- /dev/null
+++ b/templates/.envrc
@@ -0,0 +1,10 @@
+nix_direnv_watch_file package-lock.json
+use flake ..#templates
+
+# Update package.json
+if ! cmp --silent .checksum-package.yaml <(sha256sum package.yaml); then
+    echo "Updating package.json"
+    unlink ./package.json
+    yj < ./package.yaml > ./package.json
+    sha256sum package.yaml > .checksum-package.yaml
+fi
diff --git a/templates/.gitignore b/templates/.gitignore
index e349813..d6989d1 100644
--- a/templates/.gitignore
+++ b/templates/.gitignore
@@ -3,3 +3,4 @@ dist/
 node_modules/
 package.json
 result
+.checksum-package.yaml