ictus articulation incorrectly placed

[Roman Stawski]

Hi folks

There seems to be a problem with the placing of ictus articulation in
the following example

--
\version "2.13.18"
\include "gregorian.ly"

\new VaticanaVoice \relative c' {
  \[ a c\ictus \pes e \]
}
--

The ictus is output below the first note rather than below the second
and to the side of the first. The following images show what I'm trying
to get:

http://www.musique-liturgique.com/images/stories/Apprentissage/salicus.png

http://lphrc.org/Chant/salicus.gif

I see that issue 316 which also talks about about ictus rendering has
been postponed. Is ancient notation still maintained?

Roman