diff --git a/package.json b/package.json
index bc7ea27..7d16f0a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "isolate-package",
-  "version": "1.20.0-1",
+  "version": "1.20.0-2",
   "description": "Isolate a monorepo package with its shared dependencies to form a self-contained directory, compatible with Firebase deploy",
   "author": "Thijs Koerselman",
   "license": "MIT",
@@ -40,7 +40,7 @@
     "lint": "eslint . --max-warnings 0",
     "lint:format": "prettier --check .",
     "compile": "tsc --noEmit",
-    "prepare": "pnpm run compile && pnpm run build"
+    "?prepare": "pnpm run compile && pnpm run build"
   },
   "dependencies": {
     "@npmcli/arborist": "^7.5.4",
diff --git a/src/lib/lockfile/helpers/generate-npm-lockfile.ts b/src/lib/lockfile/helpers/generate-npm-lockfile.ts
index 11584c1..4c46c12 100644
--- a/src/lib/lockfile/helpers/generate-npm-lockfile.ts
+++ b/src/lib/lockfile/helpers/generate-npm-lockfile.ts
@@ -21,11 +21,14 @@ export async function generateNpmLockfile({
 
   log.debug("Generating NPM lockfile...");
 
-  const nodeModulesPath = path.join(workspaceRootDir, "node_modules");
+  const originalLockfilePath = path.join(workspaceRootDir, "package-lock.json");
+  const isolatedLockfilePath = path.join(isolateDir, "package-lock.json");
 
   try {
-    if (!fs.existsSync(nodeModulesPath)) {
-      throw new Error(`Failed to find node_modules at ${nodeModulesPath}`);
+    if (!fs.existsSync(originalLockfilePath)) {
+      throw new Error(
+        `Failed to find package-lock.json at ${originalLockfilePath}`
+      );
     }
 
     const config = await loadNpmConfig({ npmPath: workspaceRootDir });
@@ -35,15 +38,26 @@ export async function generateNpmLockfile({
       ...config.flat,
     });
 
+    /**
+     * One way to get NPM to match the lockfile versions seems to be to copy the
+     * original lockfile to the isolate directory and run loadVirtual before
+     * buildIdealTree
+     */
+    await fs.copy(originalLockfilePath, isolatedLockfilePath, {
+      overwrite: true,
+    });
+
+    log.debug("Load virtual tree");
+    await arborist.loadVirtual();
+
+    log.debug("Build ideal tree");
     const { meta } = await arborist.buildIdealTree();
 
     meta?.commit();
 
-    const lockfilePath = path.join(isolateDir, "package-lock.json");
-
-    await fs.writeFile(lockfilePath, String(meta));
+    await fs.writeFile(isolatedLockfilePath, String(meta));
 
-    log.debug("Created lockfile at", lockfilePath);
+    log.debug("Created lockfile at", isolatedLockfilePath);
   } catch (err) {
     log.error(`Failed to generate lockfile: ${getErrorMessage(err)}`);
     throw err;