diff --git a/app.py b/app.py
index 3c4176e..02c96de 100644
--- a/app.py
+++ b/app.py
@@ -1570,7 +1570,8 @@ def apply_headers(response):
 
     # --- statyczne pliki (nagłówki z .env) ---
     if request.path.startswith(("/static/", "/uploads/")):
-        response.headers["Vary"] = "Accept-Encoding"
+        response.headers.pop('Vary', None) # fix bug with backslash
+        response.headers['Vary'] = 'Accept-Encoding'  
         return response
 
     # --- healthcheck ---