Accidentals displaying incorrectly when second voice doubles the first

Attached snippet can be used to reproduce. Voice one has a rising chromatic line, d, e, f natural, f sharp (f sharp is in the key signature). This displays correctly.
If Voice 2 is added to double this line, none of the accidentals display, neither the natural nor the sharp that cancels the natural.
Based on the midi playback, the actual notes are correct.
In the attachment, the Voice 1 line is identical in the 4 measures. You can see how the addition of Voice 2 in measure 2 results in the incorrect accidentals. You can try adding the Voice 2 notes yourself in the following measures.
This was found in version 1.0. Revision 3996, on Windows 7 64 bit.