diff --git a/src/testdir/test_backup.vim b/src/testdir/test_backup.vim
index ce2bfe7..0d3e79c 100644
--- a/src/testdir/test_backup.vim
+++ b/src/testdir/test_backup.vim
@@ -1,5 +1,7 @@
 " Tests for the backup function
 
+source check.vim
+
 func Test_backup()
   set backup backupdir=. backupskip=
   new
@@ -56,3 +58,18 @@
   call delete(f)
   set backup&vim backupdir&vim backupcopy&vim backupskip&vim
 endfunc
+
+" Test for using a non-existing directory as a backup directory
+func Test_non_existing_backupdir()
+  CheckNotBSD
+  let save_backup = &backupdir
+  set backupdir=./non_existing_dir
+  call writefile(['line1'], 'Xfile')
+  new Xfile
+  " TODO: write doesn't fail in Cirrus FreeBSD CI test
+  call assert_fails('write', 'E510:')
+  let &backupdir = save_backup
+  call delete('Xfile')
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab