diff --git a/radicale/__init__.py b/radicale/__init__.py
index 06354d9..c5266e8 100644
--- a/radicale/__init__.py
+++ b/radicale/__init__.py
@@ -338,7 +338,7 @@ class Application:
             user = self.Auth.map_login_to_user(login)
         else:
             user = self.Auth.map_login_to_user(environ.get("REMOTE_USER", ""))
-            password = None
+            password = ""
 
         # If "/.well-known" is not available, clients query "/"
         if path == "/.well-known" or path.startswith("/.well-known/"):