diff --git a/titles/sao/index.py b/titles/sao/index.py
index a6ca141..b70f02a 100644
--- a/titles/sao/index.py
+++ b/titles/sao/index.py
@@ -123,9 +123,16 @@ class SaoServlet(BaseServlet):
         if resp is None:
             resp = SaoNoopResponse(req_header.cmd + 1).make()
         
+        if type(resp) == bytes:
+            pass
+        
         elif issubclass(resp, SaoBaseResponse):
             resp = resp.make()
         
+        else:
+            self.logger.error(f"Unknown response type {type(resp)}")
+            return b""
+        
         self.logger.debug(f"Response: {resp.hex()}")
 
         if self.game_cfg.crypt.enable: