diff --git a/third_party/semi_physical_train/semi_physical_train.go b/third_party/semi_physical_train/semi_physical_train.go
index 144ceba..a3a3d04 100644
--- a/third_party/semi_physical_train/semi_physical_train.go
+++ b/third_party/semi_physical_train/semi_physical_train.go
@@ -94,9 +94,12 @@ func (s *semiPhysicalTrainImpl) Stop() {
 }
 
 func (s *semiPhysicalTrainImpl) SendTrainControlMessage(info *message.DynamicsTrainInfo) {
-	sendMsg := &message.TrainSpeedMsg{}
-	sendMsg.DynamicsDecode(info)
-	s.trainSpeedInfoUdpClient.Send(sendMsg.Encode())
+	if s.trainSpeedInfoUdpClient != nil {
+		sendMsg := &message.TrainSpeedMsg{}
+		sendMsg.DynamicsDecode(info)
+		s.trainSpeedInfoUdpClient.Send(sendMsg.Encode())
+	}
+
 }
 
 func (s *semiPhysicalTrainImpl) initSemiPhysical() {