Undoing New All parts removes them one at a time

1. Open score.
2. 'File'>'Parts…'.
3. 'New All'.
4. 'OK'.
5. 'Undo'.

Expected result: All instruments removed at once.
Actual result: Part is removed one at a time.

Using MuseScore 2.0 Nightly Build (7cd411a) - Mac 10.7.5.