diff --git a/mandelstudio/middleware_language_redirect.py b/mandelstudio/middleware_language_redirect.py
index cb3ad94..d203df2 100644
--- a/mandelstudio/middleware_language_redirect.py
+++ b/mandelstudio/middleware_language_redirect.py
@@ -2,7 +2,10 @@ from __future__ import annotations
 
 from django.conf import settings
 from django.http import HttpRequest, HttpResponseRedirect
-from django.utils.translation import get_language_from_request
+from django.utils.translation import (
+    get_language_from_request,
+    get_supported_language_variant,
+)
 
 
 class FirstVisitLanguageRedirectMiddleware:
@@ -75,6 +78,22 @@ class FirstVisitLanguageRedirectMiddleware:
 
     def _preferred_language(self, request: HttpRequest) -> str | None:
         matched = get_language_from_request(request, check_path=False)
-        if not matched:
-            return None
-        return matched.split("-")[0].lower()
+        if matched:
+            normalized = matched.split("-")[0].lower()
+            if normalized in self.supported_languages and normalized != self.default_language:
+                return normalized
+
+        # Fallback to raw Accept-Language parsing for unprefixed default routes.
+        header = request.META.get("HTTP_ACCEPT_LANGUAGE", "")
+        for item in header.split(","):
+            raw_lang = item.split(";", 1)[0].strip()
+            if not raw_lang:
+                continue
+            try:
+                variant = get_supported_language_variant(raw_lang)
+            except LookupError:
+                continue
+            normalized = variant.split("-")[0].lower()
+            if normalized in self.supported_languages:
+                return normalized
+        return None