diff --git a/lib/lockfileV1/tree.js b/lib/lockfileV1/tree.js
index d07cde3..7995499 100644
--- a/lib/lockfileV1/tree.js
+++ b/lib/lockfileV1/tree.js
@@ -21,7 +21,7 @@ const {
 
 module.exports = {
   buildYarnTree (nodeModulesTree, packageLock) {
-    const flattenedPackageLock = flattenPackageLock(packageLock.dependencies)
+    const flattenedPackageLock = flattenPackageLock(packageLock.dependencies || packageLock.packages)
     const tree = Object.keys(nodeModulesTree).reduce((tree, path) => {
       const nmEntry = nodeModulesTree[path]
       const { name } = nmEntry
diff --git a/package.json b/package.json
index b8956d0..ee3ecdb 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "synp",
-  "version": "1.9.10",
+  "version": "1.9.11",
   "description": "Convert yarn.lock to package-lock.json and vice versa",
   "keywords": [
     "yarn",