diff --git a/lib/workers/branch/lock-files.js b/lib/workers/branch/lock-files.js
index 1efc267ddc5582e5329e5a97ac2812fae283dd6a..f6f74a95d48281edb1a0d992f09bf60dd70a2886 100644
--- a/lib/workers/branch/lock-files.js
+++ b/lib/workers/branch/lock-files.js
@@ -139,7 +139,7 @@ async function writeUpdatedPackageFiles(config) {
   for (const packageFile of config.updatedPackageFiles) {
     logger.debug(`Writing ${packageFile.name}`);
     const massagedFile = JSON.parse(packageFile.contents);
-    if (!massagedFile.name.match(/^[0-9a-z-_]+$/)) {
+    if (massagedFile.name && !massagedFile.name.match(/^[0-9a-z-_]+$/)) {
       massagedFile.name = 'dummy';
     }
     delete massagedFile.engines;