add override to GetPollCount() function
diff --git a/test/cpp/qps/client_async.cc b/test/cpp/qps/client_async.cc
index 05756f0..63da1e7 100644
--- a/test/cpp/qps/client_async.cc
+++ b/test/cpp/qps/client_async.cc
@@ -209,7 +209,7 @@
     }
   }
 
-  int GetPollCount() {
+  int GetPollCount() override {
     int count = 0;
     for (auto cq = cli_cqs_.begin(); cq != cli_cqs_.end(); cq++) {
       count += (int)grpc_get_cq_poll_num((*cq)->cq());
diff --git a/test/cpp/qps/server_async.cc b/test/cpp/qps/server_async.cc
index 7d00cb3..57f45d3 100644
--- a/test/cpp/qps/server_async.cc
+++ b/test/cpp/qps/server_async.cc
@@ -158,7 +158,7 @@
     shutdown_thread.join();
   }
 
-  int GetPollCount() {
+  int GetPollCount() override {
     int count = 0;
     for (auto cq = srv_cqs_.begin(); cq != srv_cqs_.end(); cq++) {
       count += (int)grpc_get_cq_poll_num((*cq)->cq());