diff --git a/api/derive.ts b/api/derive.ts
index b5de482..bf2bfa2 100644
--- a/api/derive.ts
+++ b/api/derive.ts
@@ -401,7 +401,19 @@ async function buildVideo(
 
 /** Every file under `originals/`, relative to it, depth first. Directories are structure, not work. */
 export async function listOriginals(root: string, prefix = ''): Promise<string[]> {
-  const entries = await readdir(join(root, prefix), { withFileTypes: true }).catch(() => []);
+  /*
+    Sorted, because `readdir` is not.
+
+    It returns entries in the filesystem's own order — inode order on ext4 — which is arbitrary and
+    stable only until somebody moves a file. That is harmless for the sync, which does the same work in
+    any order, and it is not harmless for "Create Gallery": this list becomes the gallery's initial
+    order, and nine photographs arriving as 05, 08, 01, 07 reads as a bug even though nothing is wrong.
+
+    `numeric` so `galeria2` sorts before `galeria10`, which is what anybody naming files that way means.
+  */
+  const entries = (await readdir(join(root, prefix), { withFileTypes: true }).catch(() => [])).sort((a, b) =>
+    a.name.localeCompare(b.name, undefined, { numeric: true, sensitivity: 'base' }),
+  );
   const found: string[] = [];
 
   for (const entry of entries) {