diff --git a/taichi/gui/gui.h b/taichi/gui/gui.h
index 1cc378e82c803..76b4406ebd3d4 100644
--- a/taichi/gui/gui.h
+++ b/taichi/gui/gui.h
@@ -428,7 +428,7 @@ class GUIBaseX11 {
   void *visual;
   unsigned long window;
   CXImage *img;
-  void *wmDeleteMessage;
+  std::vector<char> wmDeleteMessage;
 };
 
 using GUIBase = GUIBaseX11;
diff --git a/taichi/gui/x11.cpp b/taichi/gui/x11.cpp
index b3e3ac69faff2..6b735c334c720 100644
--- a/taichi/gui/x11.cpp
+++ b/taichi/gui/x11.cpp
@@ -76,7 +76,7 @@ void GUI::process_event() {
         break;
       case ClientMessage:
         // https://stackoverflow.com/questions/10792361/how-do-i-gracefully-exit-an-x11-event-loop
-        if (ev.xclient.data.l[0] == *(Atom *)wmDeleteMessage) {
+        if (ev.xclient.data.l[0] == *(Atom *)wmDeleteMessage.data()) {
           key_events.push_back(
               KeyEvent{KeyEvent::Type::press, "WMClose", cursor_pos});
           should_close++;
@@ -123,10 +123,10 @@ void GUI::create_window() {
                ButtonPressMask | ExposureMask | KeyPressMask | KeyReleaseMask |
                    ButtonPress | ButtonReleaseMask | EnterWindowMask |
                    LeaveWindowMask | PointerMotionMask);
-  wmDeleteMessage = std::malloc(sizeof(Atom));
-  *(Atom *)wmDeleteMessage =
+  wmDeleteMessage = std::vector<char>(sizeof(Atom));
+  *(Atom *)wmDeleteMessage.data() =
       XInternAtom((Display *)display, "WM_DELETE_WINDOW", False);
-  XSetWMProtocols((Display *)display, window, (Atom *)wmDeleteMessage, 1);
+  XSetWMProtocols((Display *)display, window, (Atom *)wmDeleteMessage.data(), 1);
   XMapWindow((Display *)display, window);
   img = new CXImage((Display *)display, (Visual *)visual, width, height);
 }
@@ -143,7 +143,6 @@ void GUI::set_title(std::string title) {
 
 GUI::~GUI() {
   XCloseDisplay((Display *)display);
-  std::free(wmDeleteMessage);
   delete img;
 }