diff --git a/README.md b/README.md
index 422e5d5..f8fb8a9 100644
--- a/README.md
+++ b/README.md
@@ -1099,8 +1099,7 @@ in-flight fetches by key, and an idle pool never lends its slots to a busy one.
 `lib.backup()`, and so `quak backup`, works on up to the content pool's limit of
 originals at once, 5 unless the library was opened with other `pools`. The limit
 covers everything it does for one original, hashing it for `verify` included, so
-however large the account is, no more originals than that are open at once. With
-`includeThumbnails`, it fetches the thumbnails one at a time.
+however large the account is, no more originals than that are open at once.
 
 ### On-disk cache layout
 
diff --git a/src/backup.ts b/src/backup.ts
index bbb7d7c..db39266 100644
--- a/src/backup.ts
+++ b/src/backup.ts
@@ -657,8 +657,7 @@ const runLockedBackup = async (
     // present original is hashed first, and one that does not match the hash
     // its metadata records is removed and fetched like a missing one. One
     // that cannot be read is recorded as failed and left where it is.
-    // `storeOriginal` does this for one original, and records its failure
-    // rather than throwing.
+    // `storeOriginal` does this for one original, and records its failure.
     const storeOriginal = async (file: EnteFile): Promise<void> => {
         let stored = storedAtSavePath(downloadDirectory, file);
         let mismatch = false;
@@ -731,15 +730,20 @@ const runLockedBackup = async (
     // Up to the content pool's limit of originals are worked on at once,
     // their `verify` hashing included, so however large the account is, no
     // more than that many are open. Each worker takes the next file from the
-    // iterator they all share until none is left.
+    // iterator they all share until none is left. A worker that throws, as
+    // one does when `onProgress` throws, fails the backup only once every
+    // worker has stopped, so none writes into the backup after it has ended.
     if (includeOriginals) {
         const pending = distinct.values();
         const worker = async (): Promise<void> => {
             for (const file of pending) await storeOriginal(file);
         };
-        await Promise.all(
+        const workers = await Promise.allSettled(
             Array.from({ length: lib.contentConcurrency }, worker),
         );
+        for (const w of workers) {
+            if (w.status === "rejected") throw w.reason;
+        }
     }
 
     if (includeThumbnails) {