Empty measure renders poorly at beginning of system with key signature

Ubuntu Studio 14.04, GIT commit: ca5ec50

1) new score for flute, 100 measures
2) drag G major key signature to measure 20 (or any measure on second system)

Result: display of first measure of third and subsequent systems is messed up badly:

This only affects key signatures other than an initial key signature. It also only affects full measure rests; measure with other content display normally.