diff --git a/lib/workers/branch/lock-files.js b/lib/workers/branch/lock-files.js
index 46fe54acae5a7dec35c5394a29501ce2c890ff8e..4347dbd8a6642405bf75acbba17aefe7673b0750 100644
--- a/lib/workers/branch/lock-files.js
+++ b/lib/workers/branch/lock-files.js
@@ -107,12 +107,20 @@ function determineLockFileDirs(config) {
     }
   }
 
-  if (config.updatedPackageFiles.length && config.lernaLockFile) {
+  if (
+    config.updatedPackageFile &&
+    config.updatedPackageFiles.length &&
+    config.lernaLockFile
+  ) {
     lernaDirs.push('.');
   }
 
   // If yarn workspaces are in use, then we need to generate yarn.lock from the workspaces dir
-  if (config.updatedPackageFiles.length && config.workspaceDir) {
+  if (
+    config.updatedPackageFiles &&
+    config.updatedPackageFiles.length &&
+    config.workspaceDir
+  ) {
     const updatedPackageFileNames = config.updatedPackageFiles.map(p => p.name);
     for (const packageFile of config.packageFiles) {
       if (