diff --git a/src/dwarfs/worker_group.cpp b/src/dwarfs/worker_group.cpp
index 2ca30cd7..5ea9eb0c 100644
--- a/src/dwarfs/worker_group.cpp
+++ b/src/dwarfs/worker_group.cpp
@@ -62,7 +62,7 @@ class basic_worker_group : public worker_group::impl, private Policy {
     for (size_t i = 0; i < num_workers; ++i) {
       workers_.emplace_back([=] {
         folly::setThreadName(folly::to<std::string>(group_name, i + 1));
-        static_cast<void>(::nice(niceness));
+        [[maybe_unused]] auto rv = ::nice(niceness);
         do_work();
       });
     }