1 files changed, 3 insertions, 1 deletions

diff --git a/src/window.c b/src/window.c
index 966960edd90..5dced198811 100644
--- a/src/window.c
+++ b/src/window.c
@@ -6798,7 +6798,9 @@ foreach_window (f, fn, user_data)
      int (* fn) P_ ((struct window *, void *));
      void *user_data;
 {
-  foreach_window_1 (XWINDOW (FRAME_ROOT_WINDOW (f)), fn, user_data);
+  /* Fdelete_frame may set FRAME_ROOT_WINDOW (f) to Qnil.  */
+  if (WINDOWP (FRAME_ROOT_WINDOW (f)))
+    foreach_window_1 (XWINDOW (FRAME_ROOT_WINDOW (f)), fn, user_data);
 }