python · fedonman · Aug 15, 2026
diff --git a/Doc/library/curses.panel.rst b/Doc/library/curses.panel.rst
@@ -116,6 +116,8 @@ Panel objects
 .. method:: panel.replace(win)
 
    Change the window associated with the panel to the window *win*.
+   Raise :exc:`curses.panel.error` if *win* has been detached from its
+   screen by :meth:`screen.close() <curses.screen.close>`.
 
 
 .. method:: panel.set_userptr(obj)

diff --git a/Lib/test/test_curses.py b/Lib/test/test_curses.py
@@ -3079,6 +3079,22 @@ def test_close(self):
         # close() is idempotent.
         screen.close()
 
+    @requires_curses_func('panel')
+    def test_close_then_panel_replace(self):
+        # A detached window has no underlying curses window, so replace()
+        # must reject it.  It used to be accepted, and the panel then
+        # crashed inside curses on its next use.
+        s = self.make_pty()
+        screen = curses.newterm('xterm', s, s)
+        win = screen.stdscr
+        panel = curses.panel.new_panel(curses.newwin(3, 6, 0, 0))
+        # Drop the panel from the global stack before later tests inspect it.
+        self.addCleanup(gc_collect)
+        screen.close()
+        self.assertRaises(curses.panel.error, panel.replace, win)
+        # The panel kept its own window, so it still works.
+        panel.move(1, 1)
+
     @unittest.skipUnless(hasattr(curses, 'new_prescr'),
                          'requires curses.new_prescr()')
     def test_new_prescr(self):

diff --git a/Modules/_curses_panel.c b/Modules/_curses_panel.c
@@ -594,6 +594,12 @@ _curses_panel_panel_replace_impl(PyCursesPanelObject *self,
         return NULL;
     }
 
+    if (win->win == NULL) {
+        _curses_panel_state *state = get_curses_panel_state_by_panel(self);
+        PyErr_SetString(state->error, "the window has been detached");
+        return NULL;
+    }
+
     int rtn = replace_panel(self->pan, win->win);
     if (rtn == ERR) {
         curses_panel_panel_set_error(self, "replace_panel", "replace");