diff --git a/kitty/boss.py b/kitty/boss.py
index ea7cd833c..7c54b96d3 100644
--- a/kitty/boss.py
+++ b/kitty/boss.py
@@ -224,11 +224,11 @@ class Boss:
 
     def on_os_window_closed(self, os_window_id, viewport_width, viewport_height):
         cached_values['window-size'] = viewport_width, viewport_height
-        for window_id in tuple(w.id for w in self.window_id_map.values() if getattr(w, 'os_window_id', None) == os_window_id):
-            self.window_id_map.pop(window_id, None)
         tm = self.os_window_map.pop(os_window_id, None)
         if tm is not None:
             tm.destroy()
+        for window_id in tuple(w.id for w in self.window_id_map.values() if getattr(w, 'os_window_id', None) == os_window_id):
+            self.window_id_map.pop(window_id, None)
 
     def display_scrollback(self, data):
         if self.opts.scrollback_in_new_tab:
@@ -263,6 +263,7 @@ class Boss:
         self.child_monitor.shutdown()
         wakeup()
         self.child_monitor.join()
+        del self.child_monitor
         for tm in self.os_window_map.values():
             tm.destroy()
         self.os_window_map = {}
diff --git a/kitty/child-monitor.c b/kitty/child-monitor.c
index 15ce45151..0cdbfc171 100644
--- a/kitty/child-monitor.c
+++ b/kitty/child-monitor.c
@@ -336,11 +336,8 @@ parse_input(ChildMonitor *self) {
     }
 }
 
-static PyObject *
-mark_for_close(ChildMonitor *self, PyObject *args) {
-#define mark_for_close_doc "Mark a child to be removed from the child monitor"
-    unsigned long window_id;
-    if (!PyArg_ParseTuple(args, "k", &window_id)) return NULL;
+static inline void
+mark_child_for_close(ChildMonitor *self, id_type window_id) {
     children_mutex(lock);
     for (size_t i = 0; i < self->count; i++) {
         if (children[i].id == window_id) {
@@ -350,6 +347,15 @@ mark_for_close(ChildMonitor *self, PyObject *args) {
     }
     children_mutex(unlock);
     wakeup_io_loop();
+}
+
+
+static PyObject *
+mark_for_close(ChildMonitor *self, PyObject *args) {
+#define mark_for_close_doc "Mark a child to be removed from the child monitor"
+    id_type window_id;
+    if (!PyArg_ParseTuple(args, "K", &window_id)) return NULL;
+    mark_child_for_close(self, window_id);
     Py_RETURN_NONE;
 }
 
@@ -640,8 +646,12 @@ main_loop(ChildMonitor *self) {
         for (size_t w = global_state.num_os_windows; w > 0; w--) {
             OSWindow *os_window = global_state.os_windows + w - 1;
             if (should_os_window_close(os_window)) {
-                int viewport_width, viewport_height;
-                if (remove_os_window(os_window->id, &viewport_width, &viewport_height)) call_boss(on_os_window_closed, "Kii", os_window->id, viewport_width, viewport_height);
+                call_boss(on_os_window_closed, "Kii", os_window->id, os_window->viewport_width, os_window->viewport_width);
+                for (size_t t=0; t < os_window->num_tabs; t++) {
+                    Tab *tab = os_window->tabs + t;
+                    for (size_t w = 0; w < tab->num_windows; w++) mark_child_for_close(self, tab->windows[w].id);
+                }
+                remove_os_window(os_window->id); 
             } else has_open_windows = true;
         }
     }
diff --git a/kitty/state.c b/kitty/state.c
index 59c10e969..9cfee1d09 100644
--- a/kitty/state.c
+++ b/kitty/state.c
@@ -145,7 +145,7 @@ remove_window(id_type os_window_id, id_type tab_id, id_type id) {
 
 static inline void
 destroy_tab(Tab *tab) {
-    for (size_t i = tab->num_windows; i > 0; i--) remove_window_inner(tab, tab->windows[ i - 1].id);
+    for (size_t i = tab->num_windows; i > 0; i--) remove_window_inner(tab, tab->windows[i - 1].id);
     remove_vao(tab->border_rects.vao_idx);
     free(tab->border_rects.rect_buf); tab->border_rects.rect_buf = NULL;
     free(tab->windows); tab->windows = NULL;
@@ -175,11 +175,10 @@ destroy_os_window(OSWindow *w) {
 }
 
 bool
-remove_os_window(id_type os_window_id, int *viewport_width, int *viewport_height) {
+remove_os_window(id_type os_window_id) {
     bool found = false;
     WITH_OS_WINDOW(os_window_id)
         remove_os_window_reference(os_window);
-        *viewport_width = os_window->viewport_width; *viewport_height = os_window->viewport_height;
         found = true;
     END_WITH_OS_WINDOW
     if (found) { 
diff --git a/kitty/state.h b/kitty/state.h
index 793709d5d..70c5b4ede 100644
--- a/kitty/state.h
+++ b/kitty/state.h
@@ -127,7 +127,7 @@ extern GlobalState global_state;
 
 void gl_init();
 void remove_vao(ssize_t vao_idx);
-bool remove_os_window(id_type os_window_id, int*, int*);
+bool remove_os_window(id_type os_window_id);
 void remove_os_window_reference(OSWindow *w);
 void mark_os_window_for_close(OSWindow* w, bool yes);
 bool should_os_window_close(OSWindow* w);
diff --git a/kitty/tabs.py b/kitty/tabs.py
index 73c6b6b1f..cab29f04e 100644
--- a/kitty/tabs.py
+++ b/kitty/tabs.py
@@ -419,4 +419,5 @@ class TabManager:  # {{{
             t.destroy()
         self.tab_bar.destroy()
         del self.tab_bar
+        del self.tabs
 # }}}