diff -r 4ce8df2311f0 -r 6ca1ef6c8107 ui/motif/window.c
--- a/ui/motif/window.c	Sun Nov 23 10:39:51 2025 +0100
+++ b/ui/motif/window.c	Sun Nov 23 10:49:24 2025 +0100
@@ -87,6 +87,13 @@
         ui_get_window_default_width(&window_width, &window_height);
     }
     
+    UiMotifAppWindow *appwindow = cxZalloc(a, sizeof(UiMotifAppWindow));
+    // Because we store appwindow as userdata in the widget, we use this
+    // magic field to check, if the pointer is actually the correct type.
+    // This is a dubious technique, but this is only the last defense
+    // mechanism against someone using the API wrong.
+    appwindow->magic = UI_MOTIF_APP_WINDOW;
+    
     Arg args[16];
     int n = 0;
     XtSetArg(args[n], XmNtitle, title); n++;
@@ -94,6 +101,7 @@
     XtSetArg(args[n], XmNminHeight, 50); n++;
     XtSetArg(args[n], XmNwidth, window_width); n++;
     XtSetArg(args[n], XmNheight, window_height); n++;
+    XtSetArg(args[n], XmNuserData, appwindow); n++;
     
     Widget toplevel = XtAppCreateShell(
             ui_appname(),
@@ -123,7 +131,7 @@
     
     // menu
     if(!simple) {
-        ui_create_menubar(obj, window);
+        appwindow->menubar = ui_create_menubar(obj, window);
     }
     
     // content frame
@@ -166,7 +174,17 @@
 }
 
 void ui_window_menubar_set_visible(UiObject *obj, UiBool visible) {
-    
+    UiMotifAppWindow *window = NULL;
+    XtVaGetValues(obj->widget, XmNuserData, &window, NULL);
+    if(window) {
+        if(window->magic != UI_MOTIF_APP_WINDOW) {
+            fprintf(stderr, "Error: obj is not an app window\n");
+            return;
+        }
+        if(window->menubar) {
+            ui_set_visible(window->menubar, visible);
+        }
+    }
 }
 
 static void filedialog_event(UiEventData *event, int result, UiFileList flist) {