Transpose by Key from G major to Cb major inconsistency

Steps to reproduce
1. create a new score in G major
2. Add a G major triad (G-B-D)
3. Edit > Select All
4. Notes > Transpose...
5. choose > Cb major
6. Mark "Transpose key signatures"
7. Press "OK"

Expected behavior: Key signature should be Cb major

Actual behavior: Although the notes are in Cb major, the key signature has simplified to B major

Discussion: Even though B major is enharmonically equivalent to Cb major, it probably shouldn't try to simplify the key since I specifically chose Cb major.

MuseScore version: r.2849 nightly

(Operating System: Windows 7)