diff --git a/test/cpp/util/metrics_server.cc b/test/cpp/util/metrics_server.cc
index 8db22fbecfe455a09a90ffc5425994303017ab43..426295f9b441e1952cc2b6da920a55dd39515baa 100644
--- a/test/cpp/util/metrics_server.cc
+++ b/test/cpp/util/metrics_server.cc
@@ -102,7 +102,7 @@ std::shared_ptr<Gauge> MetricsServiceImpl::CreateGauge(const grpc::string& name,
 std::unique_ptr<grpc::Server> MetricsServiceImpl::StartServer(int port) {
   gpr_log(GPR_INFO, "Building metrics server..");
 
-  grpc::string address = "0.0.0.0:" + std::to_string(port);
+  const grpc::string address = "0.0.0.0:" + std::to_string(port);
 
   ServerBuilder builder;
   builder.AddListeningPort(address, grpc::InsecureServerCredentials());