diff --git a/dbms/src/Flash/Mpp/MPPTunnelSet.h b/dbms/src/Flash/Mpp/MPPTunnelSet.h
index 12ac179b755..ed7386ef59b 100644
--- a/dbms/src/Flash/Mpp/MPPTunnelSet.h
+++ b/dbms/src/Flash/Mpp/MPPTunnelSet.h
@@ -33,7 +33,7 @@ class MPPTunnelSetBase : private boost::noncopyable
 {
 public:
     using TunnelPtr = std::shared_ptr<Tunnel>;
-    MPPTunnelSetBase(const String & req_id)
+    explicit MPPTunnelSetBase(const String & req_id)
         : log(Logger::get("MPPTunnelSet", req_id))
     {}