diff --git a/lib/workers/branch/lock-files.js b/lib/workers/branch/lock-files.js
index 7ae4f262c98f4276759b619309a10fe8a3b845d2..1efc267ddc5582e5329e5a97ac2812fae283dd6a 100644
--- a/lib/workers/branch/lock-files.js
+++ b/lib/workers/branch/lock-files.js
@@ -102,7 +102,7 @@ async function writeExistingFiles(config) {
       logger.debug(`Writing package.json to ${basedir}`);
       // Massage the file to eliminate yarn errors
       const massagedFile = { ...packageFile.content };
-      if (!massagedFile.name.match(/^[0-9a-z-_]+$/)) {
+      if (massagedFile.name && !massagedFile.name.match(/^[0-9a-z-_]+$/)) {
         massagedFile.name = 'dummy';
       }
       delete massagedFile.engines;