diff --git a/lego/sys/rpcx/service.go b/lego/sys/rpcx/service.go
index 598f3bf23..408e958e5 100644
--- a/lego/sys/rpcx/service.go
+++ b/lego/sys/rpcx/service.go
@@ -352,18 +352,18 @@ func (this *Service) call(ctx context.Context, clusterTag string, servicePath st
 		err = fmt.Errorf("on found serviceTag:%s", clusterTag)
 		return
 	}
-	this.clientmutex.RLock()
+
 	if clientaddr = selector.Select(ctx, spath[0], serviceMethod, args); clientaddr == "" {
 		err = fmt.Errorf("on found servicePath:%s", servicePath)
+		return
+	}
+	this.clientmutex.RLock()
+	if conn, ok = this.clients[clientaddr]; !ok {
+		err = fmt.Errorf("on found clientaddr:%s", clientaddr)
 		this.clientmutex.RUnlock()
 		return
 	}
 	this.clientmutex.RUnlock()
-	if conn, ok = this.clients[clientaddr]; !ok {
-		err = fmt.Errorf("on found clientaddr:%s", clientaddr)
-		return
-	}
-
 	_call = new(client.Call)
 	_call.ServicePath = servicePath
 	_call.ServiceMethod = serviceMethod