Undo restores arpeggio, but does not play it

1. Create 4/4 piano score.
2. Create quaver and add an upward arpeggio.
3. Change the quaver to a semiquaver.
4. Undo.

Expected result: The arpeggio plays.
Actual result: It doesn't play.

Workaround: Re-add it manually.

Using MuseScore 1.0 and Mac 10.4.11.