diff --git a/server/objects/mediaTypes/Book.js b/server/objects/mediaTypes/Book.js
index 9637eb50..aaaa523e 100644
--- a/server/objects/mediaTypes/Book.js
+++ b/server/objects/mediaTypes/Book.js
@@ -439,7 +439,7 @@ class Book {
 
         includedAudioFiles.forEach((file) => {
           if (file.duration) {
-            let chapters = file.chapters?.map((c) => ({
+            const chapters = file.chapters?.map((c) => ({
               ...c,
               id: c.id + currChapterId,
               start: c.start + currStartTime,