diff --git a/lib/src/HttpServer.cc b/lib/src/HttpServer.cc
index 246e15df..0d86e2c1 100644
--- a/lib/src/HttpServer.cc
+++ b/lib/src/HttpServer.cc
@@ -182,36 +182,7 @@ void HttpServer::onMessage(const TcpConnectionPtr &conn, MsgBuffer *buf)
         req->setCreationDate(trantor::Date::date());
         req->setSecure(conn->isSSLConnection());
         req->setPeerCertificate(conn->peerCertificate());
-        if (requestParser->firstReq() && isWebSocket(req))
-        {
-            auto wsConn = std::make_shared<WebSocketConnectionImpl>(conn);
-            wsConn->setPingMessage("", std::chrono::seconds{30});
-            newWebsocketCallback_(
-                req,
-                [conn, wsConn, requestParser, this, req](
-                    const HttpResponsePtr &resp) mutable {
-                    if (conn->connected())
-                    {
-                        for (auto &advice : preSendingAdvices_)
-                        {
-                            advice(req, resp);
-                        }
-                        if (resp->statusCode() == k101SwitchingProtocols)
-                        {
-                            requestParser->setWebsockConnection(wsConn);
-                        }
-                        auto httpString =
-                            ((HttpResponseImpl *)resp.get())->renderToBuffer();
-                        conn->send(httpString);
-                        COZ_PROGRESS
-                    }
-                },
-                wsConn);
-        }
-        else
-        {
-            requests.push_back(req);
-        }
+        requests.push_back(req);
         requestParser->reset();
     }
     onRequests(conn, requests, requestParser);
@@ -248,6 +219,55 @@ void HttpServer::onRequests(
 {
     if (requests.empty())
         return;
+
+    // will only be checked for the first request
+    if (requestParser->firstReq() && requests.size() == 1 &&
+        isWebSocket(requests[0]))
+    {
+        auto &req = requests[0];
+        if (passSyncAdvices(req,
+                            requestParser,
+                            syncAdvices_,
+                            false /* Not pipelined */,
+                            false /* Not HEAD */))
+        {
+            auto wsConn = std::make_shared<WebSocketConnectionImpl>(conn);
+            wsConn->setPingMessage("", std::chrono::seconds{30});
+            newWebsocketCallback_(
+                req,
+                [conn, wsConn, requestParser, this, req](
+                    const HttpResponsePtr &resp) mutable {
+                    if (conn->connected())
+                    {
+                        for (auto &advice : preSendingAdvices_)
+                        {
+                            advice(req, resp);
+                        }
+                        if (resp->statusCode() == k101SwitchingProtocols)
+                        {
+                            requestParser->setWebsockConnection(wsConn);
+                        }
+                        auto httpString =
+                            ((HttpResponseImpl *)resp.get())->renderToBuffer();
+                        conn->send(httpString);
+                        COZ_PROGRESS
+                    }
+                },
+                wsConn);
+            return;
+        }
+
+        // flush response for not passing sync advices
+        if (conn->connected() && !requestParser->getResponseBuffer().empty())
+        {
+            sendResponses(conn,
+                          requestParser->getResponseBuffer(),
+                          requestParser->getBuffer());
+            requestParser->getResponseBuffer().clear();
+        }
+        return;
+    }
+
     if (HttpAppFrameworkImpl::instance().keepaliveRequestsNumber() > 0 &&
         requestParser->numberOfRequestsParsed() >=
             HttpAppFrameworkImpl::instance().keepaliveRequestsNumber())
@@ -283,8 +303,7 @@ void HttpServer::onRequests(
             requestParser->pushRequestToPipelining(req, isHeadMethod);
             reqPipelined = true;
         }
-        if (!syncAdvices_.empty() &&
-            !passSyncAdvices(
+        if (!passSyncAdvices(
                 req, requestParser, syncAdvices_, reqPipelined, isHeadMethod))
         {
             continue;
@@ -678,10 +697,14 @@ void HttpServer::sendResponses(
 
 static inline bool isWebSocket(const HttpRequestImplPtr &req)
 {
+    if (req->method() != Get)
+        return false;
+
     auto &headers = req->headers();
     if (headers.find("upgrade") == headers.end() ||
         headers.find("connection") == headers.end())
         return false;
+
     auto connectionField = req->getHeaderBy("connection");
     std::transform(connectionField.begin(),
                    connectionField.end(),