diff --git a/quartz/components/pages/404.tsx b/quartz/components/pages/404.tsx
index 63da2c8..dafabad 100644
--- a/quartz/components/pages/404.tsx
+++ b/quartz/components/pages/404.tsx
@@ -11,6 +11,44 @@ const NotFound: QuartzComponent = ({ cfg }: QuartzComponentProps) => {
       <h1>404</h1>
       <p>{i18n(cfg.locale).pages.error.notFound}</p>
       <a href={baseDir}>{i18n(cfg.locale).pages.error.home}</a>
+      <script
+        dangerouslySetInnerHTML={{
+          __html: `
+          if (typeof fetchData !== "undefined") {
+            fetchData.then(function(index) {
+              var base = document.querySelector("base");
+              var basePath = (base && base.getAttribute("href")) || "/";
+              if (basePath.length > 1 && basePath.endsWith("/")) {
+                basePath = basePath.slice(0, -1);
+              }
+              var pathname = window.location.pathname;
+              if (basePath.length > 1 && pathname.startsWith(basePath)) {
+                pathname = pathname.slice(basePath.length);
+              }
+              if (pathname.startsWith("/")) {
+                pathname = pathname.slice(1);
+              }
+              if (pathname.endsWith("/")) {
+                pathname = pathname.slice(0, -1);
+              }
+              // Strip .html extension if present
+              if (pathname.endsWith(".html")) {
+                pathname = pathname.slice(0, -5);
+              }
+              // Convert trailing /index to folder slug
+              if (pathname.endsWith("/index")) {
+                pathname = pathname.slice(0, -6);
+              }
+              var lowered = pathname.toLowerCase();
+              if (lowered !== pathname && index[lowered] != null) {
+                var target = basePath + (basePath.endsWith("/") ? "" : "/") + lowered;
+                window.location.replace(target);
+              }
+            });
+          }
+          `,
+        }}
+      />
     </article>
   )
 }