diff --git a/src/client/dark.js b/src/client/dark.js
index 22543aabc..f8832e76e 100644
--- a/src/client/dark.js
+++ b/src/client/dark.js
@@ -1,7 +1,9 @@
 import {Generators} from "observablehq:stdlib";
 
-for await (const dark of Generators.dark()) {
-  const {classList} = document.body;
-  classList.toggle("dark", dark);
-  classList.toggle("light", !dark);
-}
+(async () => {
+  for await (const dark of Generators.dark()) {
+    const {classList} = document.body;
+    classList.toggle("dark", dark);
+    classList.toggle("light", !dark);
+  }
+})();
diff --git a/src/client/stdlib/generators/dark.ts b/src/client/stdlib/generators/dark.ts
index 97dfcba0d..bd9457751 100644
--- a/src/client/stdlib/generators/dark.ts
+++ b/src/client/stdlib/generators/dark.ts
@@ -5,10 +5,10 @@ export function dark() {
   return observe((notify: (dark: boolean) => void) => {
     let dark: boolean | undefined;
     const probe = document.createElement("div");
-    probe.style.setProperty("transition-property", "color");
-    probe.style.setProperty("transition-duration", "0.001s");
+    probe.style.transitionProperty = "color";
+    probe.style.transitionDuration = "0.001s";
     const changed = () => {
-      const d = getComputedStyle(probe).getPropertyValue("color-scheme") === "dark";
+      const d = getComputedStyle(probe).getPropertyValue("color-scheme") === "dark"; // TODO "light dark"?
       if (dark === d) return; // only notify if changed
       notify((dark = d));
     };