diff --git a/src/cpp/server/create_default_thread_pool.cc b/src/cpp/server/create_default_thread_pool.cc
index f3b07ec..ede18cb
--- a/src/cpp/server/create_default_thread_pool.cc
+++ b/src/cpp/server/create_default_thread_pool.cc
@@ -40,8 +40,12 @@
 namespace grpc {
 
 ThreadPoolInterface* CreateDefaultThreadPool() {
+#ifdef NDEBUG
   int cores = gpr_cpu_num_cores();
   if (!cores) cores = 4;
+#else
+  int cores = 0;
+#endif
   return new DynamicThreadPool(cores);
 }