diff --git a/apps/portal-shell/src/app/app.routes.ts b/apps/portal-shell/src/app/app.routes.ts
index ef48a31..5e89e14 100644
--- a/apps/portal-shell/src/app/app.routes.ts
+++ b/apps/portal-shell/src/app/app.routes.ts
@@ -31,4 +31,16 @@ export const appRoutes: Route[] = [
     redirectTo: 'accessibility',
     pathMatch: 'full',
   },
+  // Catch-all. In production each locale ships with its own
+  // `<base href="/{locale}/">`, so the router never actually sees
+  // the locale segment — `/fr/foo` is normalised to `foo` before
+  // route matching, and unknown paths land here for a graceful
+  // bounce to home. In dev (`nx serve`) the dev server serves the
+  // source bundle for any URL, including `/fr/...`; without this
+  // fallback the router throws NG04002 trying to match `fr` as a
+  // segment.
+  {
+    path: '**',
+    redirectTo: '',
+  },
 ];