diff --git a/src/testdir/test_undo.vim b/src/testdir/test_undo.vim
index 461b28f..368ebbe 100644
--- a/src/testdir/test_undo.vim
+++ b/src/testdir/test_undo.vim
@@ -134,6 +134,18 @@
   call assert_notequal(d1, d)
   call assert_equal(d2, d)
 
+  " error cases
+  call assert_fails('call undotree(-1)', 'E158:')
+  call assert_fails('call undotree("nosuchbuf")', 'E158:')
+
+  " after creating a buffer nosuchbuf, undotree('nosuchbuf') should
+  " not error out
+  new nosuchbuf
+  let d = {'seq_last': 0, 'entries': [], 'time_cur': 0, 'save_last': 0, 'synced': 1, 'save_cur': 0, 'seq_cur': 0}
+  call assert_equal(d, undotree("nosuchbuf"))
+  " clean up
+  bw nosuchbuf
+
   " Drop created windows
   set ul&
   new