Fix makefile
diff --git a/cpp/helloworld/Makefile b/cpp/helloworld/Makefile
index 3812689..a8d01a7 100644
--- a/cpp/helloworld/Makefile
+++ b/cpp/helloworld/Makefile
@@ -43,10 +43,10 @@
 
 all: system-check greeter_client greeter_server
 
-greeter_client: helloworld.grpc.pb.o helloworld.pb.o greeter_client.o
+greeter_client: helloworld.pb.o helloworld.grpc.pb.o greeter_client.o
 	$(CXX) $^ $(LDFLAGS) -o $@
 
-greeter_server: helloworld.pb.o greeter_server.o
+greeter_server: helloworld.pb.o helloworld.grpc.pb.o greeter_server.o
 	$(CXX) $^ $(LDFLAGS) -o $@
 
 %.grpc.pb.cc: %.proto