Failed in Tensorflow Serving gRPC reflection

I'm trying to add a gRPC health check endpoint in tensorflow serving. I added these code into tensorflow_serving/model_servers/server.cc and re-compiled it:

::grpc::EnableDefaultHealthCheckService(true);
::grpc::reflection::InitProtoReflectionServerBuilderPlugin();

After that I run it and test with grpcurl: grpcurl -plaintext localhost:8500 list It shows:

grpc.health.v1.Health
grpc.reflection.v1alpha.ServerReflection 
tensorflow.ProfilerService 
tensorflow.serving.ModelService 
tensorflow.serving.PredictionService

But when I try grpcurl -plaintext localhost:8500 grpc.health.v1.Health/Check It says:

Error invoking method "grpc.health.v1.Health/Check": target server does not expose service "grpc.health.v1.Health"

It's quite a simple feature but have been stucking me for several days. Could someone help? Thanks in advance!