diff --git a/src/dwarfs/performance_monitor.cpp b/src/dwarfs/performance_monitor.cpp
index 72b321fc..bf7e85d1 100644
--- a/src/dwarfs/performance_monitor.cpp
+++ b/src/dwarfs/performance_monitor.cpp
@@ -99,8 +99,8 @@ class single_timer {
   }
 
  private:
-  std::atomic<uint64_t> samples_;
-  std::atomic<uint64_t> total_time_;
+  std::atomic<uint64_t> samples_{};
+  std::atomic<uint64_t> total_time_{};
   folly::Histogram<size_t> log_hist_;
   std::mutex mutable log_hist_mutex_;
   std::string const namespace_;