diff --git a/tools/file_packager.py b/tools/file_packager.py
index 956ab8a3530cf..9f39984b46fca 100755
--- a/tools/file_packager.py
+++ b/tools/file_packager.py
@@ -914,6 +914,10 @@ def generate_js(data_target, data_files, metadata):
           for (var chunkId = 0; chunkId < chunkCount; chunkId++) {
             var getRequest = packages.get(`package/${packageName}/${chunkId}`);
             getRequest.onsuccess = function(event) {
+              if (!event.target.result) {
+                errback(new Error(`CachedPackageNotFound for: ${packageName}`));
+                return;
+              }
               // If there's only 1 chunk, there's nothing to concatenate it with so we can just return it now
               if (chunkCount == 1) {
                 callback(event.target.result);