diff --git a/xmpp_logger.py b/xmpp_logger.py
index 5d329ca5..7eb93c82 100644
--- a/xmpp_logger.py
+++ b/xmpp_logger.py
@@ -494,9 +494,9 @@ def best_key():
         if w.get("status") != "ok": s += 100
         if m.get("status") != "ok": s += 10
         # usage 越高越差
-        s += r.get("usage_percent", 0) * 0.01
-        s += w.get("usage_percent", 0) * 0.001
-        s += m.get("usage_percent", 0) * 0.0001
+        s += (r.get("usage_percent") or 0) * 0.01
+        s += (w.get("usage_percent") or 0) * 0.001
+        s += (m.get("usage_percent") or 0) * 0.0001
         # session_expired 惩罚
         if k.get("session_expired"): s += 500
         return s