diff --git a/web/next.config.mjs b/web/next.config.mjs
index a0227d65..9ae1cfac 100644
--- a/web/next.config.mjs
+++ b/web/next.config.mjs
@@ -13,6 +13,18 @@ const withNextIntl = createNextIntlPlugin('./i18n/request.ts')
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   output: "export",
+  // GitHub Pages serves a directory URL `/foo/` by looking for
+  // `out/foo/index.html`. Next.js's default static export with
+  // `trailingSlash: false` emits `out/foo.html` instead, which Pages
+  // only serves for the bare URL `/foo` (no trailing slash). The
+  // i18n root redirect points users at `/<defaultLocale>/` (with
+  // slash) — so every visitor would land on a 404. Enabling
+  // trailingSlash makes Next.js emit `out/<route>/index.html` for
+  // every page, including `out/en/index.html` and `out/es/index.html`
+  // so the locale roots load correctly. Internal `<Link>` URLs from
+  // next-intl already include the trailing slash, so this aligns
+  // export, runtime navigation and Pages serving.
+  trailingSlash: true,
   eslint: {
     ignoreDuringBuilds: true,
   },