diff --git a/nix_update/update.py b/nix_update/update.py
index 27f8513..8f55f08 100644
--- a/nix_update/update.py
+++ b/nix_update/update.py
@@ -268,79 +268,33 @@ def update_cargo_lock(
                 print(line, end="")
 
 
-def generate_cargo_lock(opts: Options, filename: str) -> None:
-    @contextmanager
-    def disable_copystat():
-        _orig = shutil.copystat
-        shutil.copystat = lambda *args, **kwargs: None
-        try:
-            yield
-        finally:
-            shutil.copystat = _orig
-
-    getSrcAndCargo = textwrap.dedent(f"""
-      {get_package(opts)}.overrideAttrs (old: {{
-        cargoDeps = null;
-        cargoVendorDir = ".";
-        postUnpack = ''
-          cp -pr --reflink=auto -- $sourceRoot $out
-          mkdir -p "$out/nix-support"
-          command -v cargo > $out/nix-support/cargo-bin || {{
-            echo "no cargo executable found in native build inputs" >&2
-            exit 1
-          }}
-          exit
-        '';
-        outputs = [ "out" ];
-        separateDebugInfo = false;
-      }})
-    """)
-
-    res = run(
-        [
-            "nix",
-            "build",
-            "-L",
-            "--no-link",
-            "--impure",
-            "--print-out-paths",
-            "--expr",
-            getSrcAndCargo,
+def generate_lockfile(opts: Options, filename: str, type: str) -> None:
+    if type == "cargo":
+        cmd = [
+            "generate-lockfile",
+            "--manifest-path",
+            f"{opts.lockfile_metadata_path}/Cargo.toml",
         ]
-        + opts.extra_flags,
-    )
-    src = Path(res.stdout.strip())
-
-    with tempfile.TemporaryDirectory() as tempdir:
-        with disable_copystat():
-            shutil.copytree(src, tempdir, dirs_exist_ok=True, copy_function=shutil.copy)
-
-        cargo_bin = (src / "nix-support" / "cargo-bin").read_text().rstrip("\n")
-
-        run(
-            [
-                cargo_bin,
-                "generate-lockfile",
-                "--manifest-path",
-                f"{opts.lockfile_metadata_path}/Cargo.toml",
-            ],
-            cwd=tempdir,
-        )
-
-        if (
-            lockfile_in_subdir := Path(tempdir)
-            / opts.lockfile_metadata_path
-            / "Cargo.lock"
-        ).exists():
-            # if Cargo.toml is outside a workspace, Cargo.lock is generated in the same directory as Cargo.toml
-            lockfile = lockfile_in_subdir
-        else:
-            lockfile = Path(tempdir) / "Cargo.lock"
-
-        shutil.copy(lockfile, Path(filename).parent / "Cargo.lock")
-
+        bin_name = "cargo"
+        lockfile_name = "Cargo.lock"
+        extra_nix_override = """
+          cargoDeps = null;
+          cargoVendorDir = ".";
+        """
+    elif type == "npm":
+        cmd = [
+            "install",
+            "--package-lock-only",
+            "--prefix",
+            opts.lockfile_metadata_path,
+        ]
+        bin_name = "npm"
+        lockfile_name = "package-lock.json"
+        extra_nix_override = """
+          npmDeps = null;
+          npmDepsHash = null;
+        """
 
-def generate_npm_lock(opts: Options, filename: str) -> None:
     @contextmanager
     def disable_copystat():
         _orig = shutil.copystat
@@ -350,16 +304,15 @@ def disable_copystat():
         finally:
             shutil.copystat = _orig
 
-    getSrcAndNpm = textwrap.dedent(
+    getSrcAndBin = textwrap.dedent(
         f"""
       {get_package(opts)}.overrideAttrs (old: {{
-        npmDeps = null;
-        npmDepsHash = null;
+        {extra_nix_override}
         postUnpack = ''
           cp -pr --reflink=auto -- $sourceRoot $out
           mkdir -p "$out/nix-support"
-          command -v npm > $out/nix-support/npm-bin || {{
-            echo "no npm executable found in native build inputs" >&2
+          command -v {bin_name} > $out/nix-support/{bin_name}-bin || {{
+            echo "no {bin_name} executable found in native build inputs" >&2
             exit 1
           }}
           exit
@@ -379,7 +332,7 @@ def disable_copystat():
             "--impure",
             "--print-out-paths",
             "--expr",
-            getSrcAndNpm,
+            getSrcAndBin,
         ]
         + opts.extra_flags,
     )
@@ -389,30 +342,23 @@ def disable_copystat():
         with disable_copystat():
             shutil.copytree(src, tempdir, dirs_exist_ok=True, copy_function=shutil.copy)
 
-        npm_bin = (src / "nix-support" / "npm-bin").read_text().rstrip("\n")
+        bin_path = (src / "nix-support" / f"{bin_name}-bin").read_text().rstrip("\n")
 
         run(
-            [
-                npm_bin,
-                "install",
-                "--package-lock-only",
-                "--prefix",
-                opts.lockfile_metadata_path,
-            ],
+            [bin_path] + cmd,
             cwd=tempdir,
         )
 
         if (
             lockfile_in_subdir := Path(tempdir)
             / opts.lockfile_metadata_path
-            / "package-lock.json"
+            / lockfile_name
         ).exists():
-            # if package.json is outside a workspace, package0lock.json is generated in the same directory as package.json
             lockfile = lockfile_in_subdir
         else:
-            lockfile = Path(tempdir) / "package-lock.json"
+            lockfile = Path(tempdir) / lockfile_name
 
-        shutil.copy(lockfile, Path(filename).parent / "package-lock.json")
+        shutil.copy(lockfile, Path(filename).parent / lockfile_name)
 
 
 def update_composer_deps_hash(opts: Options, filename: str, current_hash: str) -> None:
@@ -585,7 +531,7 @@ def update(opts: Options) -> Package:
 
         if package.npm_deps:
             if opts.generate_lockfile:
-                generate_npm_lock(opts, package.filename)
+                generate_lockfile(opts, package.filename, "npm")
             update_npm_deps_hash(opts, package.filename, package.npm_deps)
 
         if package.pnpm_deps:
@@ -607,7 +553,7 @@ def update(opts: Options) -> Package:
             package.cargo_lock, CargoLockInStore
         ):
             if opts.generate_lockfile:
-                generate_cargo_lock(opts, package.filename)
+                generate_lockfile(opts, package.filename, "cargo")
             else:
                 update_cargo_lock(opts, package.filename, package.cargo_lock)