diff --git a/src/rollup.ts b/src/rollup.ts
index 6302b49c5..35946944c 100644
--- a/src/rollup.ts
+++ b/src/rollup.ts
@@ -214,6 +214,7 @@ export default {
       "${root}/.observablehq/cache/_import/**/*.js" /* transpiled components */
     ]
   },
+  darkMode: ["variant", "&:where([class~=dark], [class~=dark] *)"],
   prefix: 'tw-',
   ...config
 };