diff --git a/test/cpp/qps/json_run_localhost.cc b/test/cpp/qps/json_run_localhost.cc
index 409abed..b7b2553 100644
--- a/test/cpp/qps/json_run_localhost.cc
+++ b/test/cpp/qps/json_run_localhost.cc
@@ -61,7 +61,7 @@
 
 static void sighandler(int sig) {
   const int errno_saved = errno;
-  g_driver->Interrupt();
+  if (g_driver != NULL) g_driver->Interrupt();
   for (int i = 0; i < kNumWorkers; ++i) {
     if (g_workers[i]) g_workers[i]->Interrupt();
   }
@@ -133,6 +133,7 @@
   }
 
   delete g_driver;
+  g_driver = NULL;
   for (int i = 0; i < kNumWorkers; ++i) delete g_workers[i];
   GPR_ASSERT(driver_join_status == 0);
 }