diff --git a/qse/lib/si/App.cpp b/qse/lib/si/App.cpp
index 59951080..36d29895 100644
--- a/qse/lib/si/App.cpp
+++ b/qse/lib/si/App.cpp
@@ -344,7 +344,7 @@ int App::unset_signal_handler_no_mutex(int sig, int ignore)
 		if (sl._state == App::SIGNAL_ACCEPTED) 
 		{
 			// the actual signal handler is called with the mutex locked.
-			// it must not call acceptSingal()/discardSignal()neglectSingal()
+			// it must not call acceptSingal()/discardSignal()/neglectSingal()
 			// from within the handler.
 			if (app->_guarded_child_pid >= 0) app->on_guard_signal (sig);
 			app->on_signal (sig);
diff --git a/qse/lib/si/TcpServer.cpp b/qse/lib/si/TcpServer.cpp
index 419684f4..dba1c203 100644
--- a/qse/lib/si/TcpServer.cpp
+++ b/qse/lib/si/TcpServer.cpp
@@ -436,13 +436,20 @@ int TcpServer::stop () QSE_CPP_NOEXCEPT
 {
 	if (this->server_serving) 
 	{
+		// set stop request before writing "Q" to avoid race condition.
+		// after qse_mux_poll() detects activity for "Q" written,
+		// it loops over to another qse_mux_poll(). the stop request
+		// test is done in between. if this looping is faster than
+		// setting stop request after "Q" writing, the second qse_mux_poll()
+		// doesn't see it set to true yet.
+		this->setStopRequested (true);
+
 		this->listener_list.mux_pipe_spl.lock ();
 		if (this->listener_list.mux_pipe[1] >= 0)
 		{
 			::write (this->listener_list.mux_pipe[1], "Q", 1);
 		}
 		this->listener_list.mux_pipe_spl.unlock ();
-		this->setStopRequested (true);
 	}
 	return 0;
 }