diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 403f455b89..9389d866d3 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -3049,7 +3049,7 @@ int buf_check_timestamp(buf_T *buf)
   if (reload != RELOAD_NONE) {
     // Reload the buffer.
     buf_reload(buf, orig_mode, reload == RELOAD_DETECT);
-    if (buf->b_p_udf && buf->b_ffname != NULL) {
+    if (bufref_valid(&bufref) && buf->b_p_udf && buf->b_ffname != NULL) {
       uint8_t hash[UNDO_HASH_SIZE];
 
       // Any existing undo file is unusable, write it now.
diff --git a/test/old/testdir/test_filechanged.vim b/test/old/testdir/test_filechanged.vim
index a8fc78ff90..0bb20f2ddb 100644
--- a/test/old/testdir/test_filechanged.vim
+++ b/test/old/testdir/test_filechanged.vim
@@ -289,4 +289,27 @@ func Test_FileChangedShell_newbuf()
   call delete('Xfile')
 endfunc
 
+func Test_file_changed_wipeout()
+  call writefile(['foo'], 'Xchanged_bw', 'D')
+  edit Xchanged_bw
+  augroup FileChangedWipeout
+    autocmd FileChangedShell * ++once let v:fcs_choice = 'reload'
+    autocmd BufReadPost * ++once %bw!
+  augroup END
+
+  " Need to wait until the timestamp would change.
+  if has('nanotime')
+    sleep 10m
+  else
+    sleep 2
+  endif
+  call writefile(['bar'], 'Xchanged_bw')
+  call assert_equal(1, bufexists('Xchanged_bw'))
+  checktime " used to be a heap UAF
+  call assert_equal(0, bufexists('Xchanged_bw'))
+
+  au! FileChangedWipeout
+  %bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab