diff --git a/src/rtmt/rtmt_websocket.ts b/src/rtmt/rtmt_websocket.ts
index 6aaf1bd..6289357 100644
--- a/src/rtmt/rtmt_websocket.ts
+++ b/src/rtmt/rtmt_websocket.ts
@@ -83,6 +83,7 @@ export class RTMTWS extends EventEmitter2 implements RTMT {
     clearTimeout(this.pingTimeout);
     this.pingTimeout = setTimeout(() => {
       if (!this.webSocket) return;
+      console.log("(RTMT) WebSocket self closed");
       this.webSocket.close();
       this.onWebSocketClose(this.webSocket);
     }, RTMT_WS_PING_INTERVAL + RTMT_WS_PING_INTERVAL_BUFFER_TIME);