diff --git a/src/testdir/test_delete.vim b/src/testdir/test_delete.vim
index b3e153e..0ab5164 100644
--- a/src/testdir/test_delete.vim
+++ b/src/testdir/test_delete.vim
@@ -32,7 +32,7 @@
   call assert_equal(['a', 'b'], readfile('Xdir1/Xfile'))
   call assert_true(isdirectory('Xdir1/subdir'))
   call assert_equal(['a', 'b'], readfile('Xdir1/subdir/Xfile'))
-  call assert_true(isdirectory('Xdir1/empty'))
+  call assert_true('Xdir1/empty'->isdirectory())
   call assert_equal(0, delete('Xdir1', 'rf'))
   call assert_false(isdirectory('Xdir1'))
   call assert_equal(-1, delete('Xdir1', 'd'))