Painting using Qt::color1 on Format_MonoLSB QImage doesn't work

I am unable to draw text on a Mono_LSB QImage using QPainter.

I fill the QImage with color0 using QImage::fill(Qt::color0); then try to use a QPainter to draw text with color Qt::color1.

The text doesn't show up.

This used to work in versions prior to Qt 5.6.

If I change the code to use Qt::white for the text, it shows up OK.

See attached mono.zip for a reproducible test case.