diff --git a/app/api/statistik/grafik/proxy.ts b/app/api/statistik/grafik/proxy.ts
index a93b44a..311433e 100644
--- a/app/api/statistik/grafik/proxy.ts
+++ b/app/api/statistik/grafik/proxy.ts
@@ -93,7 +93,17 @@ export async function grafikProxy(req: Request, slug?: string[]) {
     });
 
     const contentType = upstream.headers.get('content-type') || outHeaders['content-type'] || '';
-    if (contentType.toLowerCase().includes('text/html')) {
+    const isHtmlResponse = contentType.toLowerCase().includes('text/html');
+
+    // JS/CSS/font assets that come back as HTML are upstream errors (404, redirect pages).
+    // Return a 404 so the browser doesn't refuse to execute them as wrong MIME type.
+    const assetExtension = /\.(js|css|woff2?|ttf|eot|png|jpg|gif|svg|ico)(\?|$)/i;
+    const requestPath = new URL(req.url).pathname;
+    if (isHtmlResponse && slug?.length && assetExtension.test(requestPath)) {
+      return new NextResponse(null, { status: 404 });
+    }
+
+    if (isHtmlResponse) {
       const text = Buffer.from(bodyBuf).toString('utf8');
       const cleaned = rewriteHtml(text);
       outHeaders['content-type'] = 'text/html; charset=utf-8';