Bracket too short

1. Open attached score (produced in 1.2).

Result: The bracket is too short.

Discussion: I'm not sure I know the rules, so I would appreciate corrections (or perhaps confirmation) to my hypothesis:

The inner corner of a bracket must clear the top and bottom lines of a stave with slight space inbetween. If there are instruments with less than 5 stave lines, the bracket should be the same size of one that normally accommodates 5 stave lines.

Using MuseScore 2.0 Nightly Build (0b00926) - Mac 10.7.5.