diff --git a/requirements.txt b/requirements.txt
index 67d9a4a..0883440 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,2 @@
-tak @ git+https://github.com/Stephenson-Software/tak@1bac386777d4b2468faeda00b31e960af8d57164
+tak @ git+https://github.com/Stephenson-Software/tak@9b539d8760e2c02cc262a7dcff6d0c541572ab71
 jsonschema
diff --git a/tests/test_web_build.py b/tests/test_web_build.py
index 250a149..fc2bcc2 100644
--- a/tests/test_web_build.py
+++ b/tests/test_web_build.py
@@ -14,6 +14,8 @@ def test_the_page_uses_the_kits_assets_and_names_the_game():
         assert asset in page, asset
     assert 'idbName: "overwinter-saves"' in page
     assert 'saveDirEnv: "OVERWINTER_SAVE_DIR"' in page
+    # Cloud saves (RFC 0016), only on arcade and only once a player turns them on.
+    assert "cloudSaves: true," in page
     assert 'entry: "web/pyodide_main.py"' in page
 
 
diff --git a/web/index.html b/web/index.html
index e42d10f..045c6a4 100644
--- a/web/index.html
+++ b/web/index.html
@@ -20,7 +20,7 @@
 <h2>Overwinter <span class="tagline">— four people, one station, twenty days until a plane</span></h2>
 <div id="status" class="status">Starting&hellip;</div>
 <div id="app"></div>
-<p class="controls">Tip: click an option or press its number key (1-9). Enter or Space continues. Your saved games live in this browser.</p>
+<p class="controls">Tip: click an option or press its number key (1-9). Enter or Space continues. Your saved games live in this browser; at overwinter.play.danielstephenson.dev you can also back them up to your account once signed in.</p>
 <footer class="credit">More by Daniel Stephenson &rarr; <a href="https://danielstephenson.dev">danielstephenson.dev</a></footer>
 <script src="/tak/client.js"></script>
 <script src="/tak/boot.js"></script>
@@ -31,6 +31,11 @@ <h2>Overwinter <span class="tagline">— four people, one station, twenty days u
   bundleUrl: "/web/game.zip",
   entry: "web/pyodide_main.py",
   logPrefix: "[overwinter]",
+  // Cloud saves on arcade (RFC 0016): a signed-in player can back these
+  // saves up and get them on their other devices. Off until they turn it on,
+  // and only on overwinter.play.danielstephenson.dev: the old alias host never
+  // loads cloud.js (tak's onArcadeHost), so its saves stay in its browser.
+  cloudSaves: true,
   messages: { download: "The plane is going away over the ridge…", start: "Morning watch…" },
 });
 </script>