diff --git a/mold.h b/mold.h
index 73fe6910d2..1dd7031988 100644
--- a/mold.h
+++ b/mold.h
@@ -543,12 +543,12 @@ struct TimerRecord {
 
   std::string name;
   TimerRecord *parent;
+  std::once_flag once;
   tbb::concurrent_vector<TimerRecord *> children;
   i64 start;
   i64 end;
   i64 user;
   i64 sys;
-  bool stopped = false;
 };
 
 void
diff --git a/perf.cc b/perf.cc
index 51e95168d3..2c60b90f53 100644
--- a/perf.cc
+++ b/perf.cc
@@ -46,16 +46,14 @@ TimerRecord::TimerRecord(std::string name, TimerRecord *parent)
 }
 
 void TimerRecord::stop() {
-  if (stopped)
-    return;
-  stopped = true;
+  std::call_once(once, [&]() {
+    struct rusage usage;
+    getrusage(RUSAGE_SELF, &usage);
 
-  struct rusage usage;
-  getrusage(RUSAGE_SELF, &usage);
-
-  end = now_nsec();
-  user = to_nsec(usage.ru_utime) - user;
-  sys = to_nsec(usage.ru_stime) - sys;
+    end = now_nsec();
+    user = to_nsec(usage.ru_utime) - user;
+    sys = to_nsec(usage.ru_stime) - sys;
+  });
 }
 
 static void print_rec(TimerRecord &rec, i64 indent) {