Playback in Custom Key

Greetings!

I just downloaded MuseScore, and am using it to document an arrangement for my bellydance troupe.

I was able to create a Custom Key Signature representing Hijaz in D, and was able to annotate my staff with it (although it doesn't show up in the Key Signature palette...I had to drag it from the 'Create...' window.

But, playback does not seem to be honoring the key signature...those notes which I have made sharp in the key signature (F#, D#, A#, in this case) are being played as naturals.

Is this a known issue?

Do I need to do something else to get playback to work correctly?

Thanks!