Fusion style: Black icon background when using stylesheet in QComboBox

When setting a background color to QComboBox with stylesheet

setStyleSheet("QComboBox{ background-color: #dedede}");

the background of the previously selected item's icon is black when hovering over the other items. This doesn't depend on set background-color, it is always black.

For comparison, in QComboBox without a stylesheet, the color is a tad darker grey than the background (i.e. merged palette background and highlight colors).

See the attached screenshots. I'll also attach a simple example to reproduce the problem.