diff --git a/src/testdir/test_writefile.vim b/src/testdir/test_writefile.vim
index e7a309a..7256c65 100644
--- a/src/testdir/test_writefile.vim
+++ b/src/testdir/test_writefile.vim
@@ -410,6 +410,9 @@
 func Test_write_readonly_dir()
   " On MS-Windows, modifying files in a read-only directory is allowed.
   CheckUnix
+  " Root can do it too.
+  CheckNotRoot
+
   call mkdir('Xdir')
   call writefile(['one'], 'Xdir/Xfile1')
   call setfperm('Xdir', 'r-xr--r--')