Lyrics disappeared from midi files in 2.4.0

[Michiel Lange]

Recently I have upgraded from lilypond 2.2 to 2.4
After convert-ly and running the files through lilypond it appears that 
songs with lyrics that did have lyrics in midifiles in lily 2.2 no 
longer have them. Has something changed around this point that passed my 
attention when reading the changedocs?

How would I get lyrics appear again in my midifiles, as I often use it 
to learn songs.

Thanks!
Michiel