diff --git a/thumbnails/Tupfile b/thumbnails/Tupfile
index faffc49..4aa8970 100644
--- a/thumbnails/Tupfile
+++ b/thumbnails/Tupfile
@@ -1,7 +1 @@
-: asset.raw |> !tup_preserve |>
-: asset.raw |> cp %f %o |> asset.thumbnail
-
-# tup error: Unable to create output file 'asset.thumbnail' because it is
-# already owned by command 16.
-#: foreach *.raw |> !tup_preserve |>
-#: foreach *.raw |> cp %f %o |> asset.thumbnail
+run ./generate_thumbnails.tup
diff --git a/thumbnails/generate_thumbnails.tup b/thumbnails/generate_thumbnails.tup
new file mode 100755
index 0000000..92e8eb1
--- /dev/null
+++ b/thumbnails/generate_thumbnails.tup
@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+for i in *.raw; do
+    echo ": $i |> !tup_preserve |>"
+    echo ": $i |> cp %f %o |> %B.thumbnail"
+done