diff --git a/src/utils/MessageQueue.cc b/src/utils/MessageQueue.cc
index 0e7f1e19..af7c6012 100644
--- a/src/utils/MessageQueue.cc
+++ b/src/utils/MessageQueue.cc
@@ -45,10 +45,7 @@ class LoopQueueGuard {
       q.erase(queue_);
     }
 
-    {
-      std::unique_lock<std::mutex> lk(queue_->queueMutex_);
-      queue_->workerCount_--;
-    }
+    queue_->workerCount_--;
     queue_->workerQuitCondition_.notify_all();
   }
 
diff --git a/src/utils/MessageQueue.h b/src/utils/MessageQueue.h
index 02ec9e53..5569a1a9 100644
--- a/src/utils/MessageQueue.h
+++ b/src/utils/MessageQueue.h
@@ -223,7 +223,7 @@ class MessageQueue {
   std::condition_variable queueNotFullCondition_;
   std::deque<Message*> queue_;
   std::atomic_int32_t messageIdCounter_;
-  size_t workerCount_;
+  std::atomic_uint32_t workerCount_;
   std::condition_variable workerQuitCondition_;
 
   std::shared_ptr<Supervisor> supervisor_;