diff --git a/src/testdir/test_excmd.vim b/src/testdir/test_excmd.vim
index f27b385..0170a9f 100644
--- a/src/testdir/test_excmd.vim
+++ b/src/testdir/test_excmd.vim
@@ -333,6 +333,7 @@
 endfunc
 
 " Test for the :redir command
+" NOTE: if you run tests as root this will fail.  Don't run tests as root!
 func Test_redir_cmd()
   call assert_fails('redir @@', 'E475:')
   call assert_fails('redir abc', 'E475:')