Prevent some compilers compaining unused return value
diff --git a/test/cpp/util/cli_call.cc b/test/cpp/util/cli_call.cc
index 98b9d93..1edffbe 100644
--- a/test/cpp/util/cli_call.cc
+++ b/test/cpp/util/cli_call.cc
@@ -94,7 +94,7 @@
 
   if (status.ok()) {
     std::vector<grpc::Slice> slices;
-    recv_buffer.Dump(&slices);
+    (void)recv_buffer.Dump(&slices);
 
     response->clear();
     for (size_t i = 0; i < slices.size(); i++) {