diff --git a/truewiki/views/sitemap.py b/truewiki/views/sitemap.py
index 5e6e65b..b987fc0 100644
--- a/truewiki/views/sitemap.py
+++ b/truewiki/views/sitemap.py
@@ -90,7 +90,7 @@ def invalidate_cache() -> None:
 def click_sitemap(frontend_url):
     global FRONTEND_URL
 
-    if frontend_url.endswith("/"):
+    if frontend_url and frontend_url.endswith("/"):
         frontend_url = frontend_url[:-1]
 
     FRONTEND_URL = frontend_url