diff --git a/frontend/src/components/Books.vue b/frontend/src/components/Books.vue
index d4067cf..e50b35d 100644
--- a/frontend/src/components/Books.vue
+++ b/frontend/src/components/Books.vue
@@ -187,7 +187,7 @@ export default {
             let authors = bs[b].authors
             for (const au in authors) {
               this.books[i].author += authors[au].forename + ' ' + authors[au].lastname
-              if (authors.length > au + 1) {
+              if ((authors.length - 1) > au) {
                 this.books[i].author += ', '
               }
             }