diff --git a/src/plugins/loader.ts b/src/plugins/loader.ts
index 5baacb089e4..d8e6393f2b6 100644
--- a/src/plugins/loader.ts
+++ b/src/plugins/loader.ts
@@ -704,6 +704,9 @@ function resolveBundledPackageCacheIdentity(stockRoot?: string):
       mtimeMs: number;
     }
   | undefined {
+  if (!stockRoot) {
+    return undefined;
+  }
   const packageRoot = resolveBundledPackageRootForCache(stockRoot);
   if (!packageRoot) {
     return undefined;