diff --git a/contentcuration/contentcuration/frontend/channelEdit/views/files/thumbnails/ThumbnailGenerator.vue b/contentcuration/contentcuration/frontend/channelEdit/views/files/thumbnails/ThumbnailGenerator.vue
index 9bb1a29f1d..e99f2e8738 100644
--- a/contentcuration/contentcuration/frontend/channelEdit/views/files/thumbnails/ThumbnailGenerator.vue
+++ b/contentcuration/contentcuration/frontend/channelEdit/views/files/thumbnails/ThumbnailGenerator.vue
@@ -158,6 +158,7 @@
           return book.loaded.cover.then(() => {
             if (!book.cover) {
               this.handleError();
+              return;
             }
             return book.archive.createUrl(book.cover, { base64: true }).then(this.handleGenerated);
           });