Transposed Chord name "F flat"

[Matthias Neeracher]

In all version of lilypond I tried (including CVS), the following 
program prints an "F flat" chord. Is this a bug, or intentional 
behavior? I would have thought this should print E instead. Same 
behavior with "C flat" vs. B.

Matthias

\version "2.3.23"

melody =  \relative c' {
        \key f \major
        c1
}

accompaniment = \chordmode { ges1 }

\score {
        \simultaneous {
          \context ChordNames \transpose f' es' \accompaniment
          \context Voice = "mel" \transpose f' es' \melody
        }

}