diff --git a/examples/cpp/helloworld/greeter_async_client.cc b/examples/cpp/helloworld/greeter_async_client.cc
index c1f5eb55f05..33de59fb957 100644
--- a/examples/cpp/helloworld/greeter_async_client.cc
+++ b/examples/cpp/helloworld/greeter_async_client.cc
@@ -87,7 +87,9 @@ class GreeterClient {
     void* got_tag;
     bool ok = false;
     // Block until the next result is available in the completion queue "cq".
-    cq.Next(&got_tag, &ok);
+    // The return value of Next should always be checked. This return value
+    // tells us whether there is any kind of event or the cq_ is shutting down.
+    GPR_ASSERT(cq.Next(&got_tag, &ok));
 
     // Verify that the result from "cq" corresponds, by its tag, our previous
     // request.
diff --git a/examples/cpp/helloworld/greeter_async_server.cc b/examples/cpp/helloworld/greeter_async_server.cc
index 64e065b1e40..ead44182e57 100644
--- a/examples/cpp/helloworld/greeter_async_server.cc
+++ b/examples/cpp/helloworld/greeter_async_server.cc
@@ -160,7 +160,9 @@ class ServerImpl final {
       // Block waiting to read the next event from the completion queue. The
       // event is uniquely identified by its tag, which in this case is the
       // memory address of a CallData instance.
-      cq_->Next(&tag, &ok);
+      // The return value of Next should always be checked. This return value
+      // tells us whether there is any kind of event or cq_ is shutting down.
+      GPR_ASSERT(cq_->Next(&tag, &ok));
       GPR_ASSERT(ok);
       static_cast<CallData*>(tag)->Proceed();
     }