diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -654,10 +654,18 @@
     if (window == this) {
       sStoredLeaveNotifyEvent = nullptr;
     }
   }
 
+  // We need to detach accessible object here because mContainer is a custom
+  // widget and doesn't call gtk_widget_real_destroy() from destroy handler
+  // as regular widgets.
+  AtkObject* ac = gtk_widget_get_accessible(GTK_WIDGET(mContainer));
+  if (ac) {
+    gtk_accessible_set_widget(GTK_ACCESSIBLE(ac), nullptr);
+  }
+
   gtk_widget_destroy(mShell);
   mShell = nullptr;
   mContainer = nullptr;
 
   MOZ_ASSERT(!mGdkWindow,