diff --git a/lib/src/HttpAppFrameworkImpl.cc b/lib/src/HttpAppFrameworkImpl.cc
index e451e02d..d2f239a0 100755
--- a/lib/src/HttpAppFrameworkImpl.cc
+++ b/lib/src/HttpAppFrameworkImpl.cc
@@ -441,6 +441,7 @@ void HttpAppFrameworkImpl::onWebsockDisconnect(const WebSocketConnectionPtr &wsC
 }
 void HttpAppFrameworkImpl::onConnection(const TcpConnectionPtr &conn)
 {
+    static std::mutex mtx;
     if (conn->connected())
     {
         if (_connectionNum.fetch_add(1) >= _maxConnectionNum)
@@ -451,14 +452,17 @@ void HttpAppFrameworkImpl::onConnection(const TcpConnectionPtr &conn)
         else if (_maxConnectionNumPerIP > 0)
         {
             {
+                std::lock_guard<std::mutex> lock(mtx);
                 auto iter = _connectionsNumMap.find(conn->peerAddr().toIp());
                 if (iter == _connectionsNumMap.end())
                 {
-                    _connectionsNumMap[conn->peerAddr().toIp()] = 0;
+                    _connectionsNumMap[conn->peerAddr().toIp()] = 1;
                 }
-                if (_connectionsNumMap[conn->peerAddr().toIp()]++ >= _maxConnectionNumPerIP)
+                else if (iter->second++ > _maxConnectionNumPerIP)
                 {
-                    conn->forceClose();
+                    conn->getLoop()->queueInLoop([conn]() {
+                        conn->forceClose();
+                    });
                 }
             }
         }
@@ -466,9 +470,18 @@ void HttpAppFrameworkImpl::onConnection(const TcpConnectionPtr &conn)
     else
     {
         _connectionNum--;
-        if (_maxConnectionNumPerIP > 0 && _connectionsNumMap.find(conn->peerAddr().toIp()) != _connectionsNumMap.end())
+        if (_maxConnectionNumPerIP > 0)
         {
-            _connectionsNumMap[conn->peerAddr().toIp()]--;
+            std::lock_guard<std::mutex> lock(mtx);
+            auto iter = _connectionsNumMap.find(conn->peerAddr().toIp());
+            if (iter != _connectionsNumMap.end())
+            {
+                iter->second--;
+                if (iter->second <= 0)
+                {
+                    _connectionsNumMap.erase(iter);
+                }
+            }
         }
     }
 }
diff --git a/lib/src/HttpAppFrameworkImpl.h b/lib/src/HttpAppFrameworkImpl.h
index 6f049919..7e05e1f9 100644
--- a/lib/src/HttpAppFrameworkImpl.h
+++ b/lib/src/HttpAppFrameworkImpl.h
@@ -184,7 +184,7 @@ class HttpAppFrameworkImpl : public HttpAppFramework
     size_t _maxConnectionNumPerIP = 0;
 
     std::atomic<uint64_t> _connectionNum;
-    std::unordered_map<std::string, std::atomic<size_t>> _connectionsNumMap;
+    std::unordered_map<std::string, size_t> _connectionsNumMap;
 
     bool _runAsDaemon = false;
     bool _relaunchOnError = false;
diff --git a/trantor b/trantor
index 50f5401a..e4da5dee 160000
--- a/trantor
+++ b/trantor
@@ -1 +1 @@
-Subproject commit 50f5401a0b97fcf94ced323d0913c2cb193f26d7
+Subproject commit e4da5dee4293475ea176a6615db0feb8bf98f833