Scrollbar background does not go solid (?) when using stylesheets

[Stukfruit]

As shown in the image attached, the following code gives me a scrollbar with a dotted background. I would like to make that background solid, but I can't seem to make Qt do that using the stylesheet mechanism.

I was wondering if someone knows if this is either a bug, if it's supposed to work like this or if there's a work-around.

I'm using Windows Vista, if that matters (I've noticed some other different behaviors as well, using Vista and Qt styles, that's why I mention it).

QScrollBar:horizontal {
	background-color: blue;
	border: 1px solid black;
	margin: 0px 16px 0px 16px;
}
 
QScrollBar::handle:horizontal {
	background: red;
	border: 1px solid yellow;
}
 
QScrollBar::add-line:horizontal {
	border: 1px solid black;
	background: purple;
	width: 16px;
	subcontrol-position: right;
	subcontrol-origin: margin;
}
 
QScrollBar::sub-line:horizontal {
	border: 1px solid black;
	background: purple;
	width: 16px;
	subcontrol-position: left;
	subcontrol-origin: margin;
}

QScrollBar:horizontal {
	background-color: blue;
	border: 1px solid black;
	margin: 0px 16px 0px 16px;
}

QScrollBar::handle:horizontal {
	background: red;
	border: 1px solid yellow;
}

QScrollBar::add-line:horizontal {
	border: 1px solid black;
	background: purple;
	width: 16px;
	subcontrol-position: right;
	subcontrol-origin: margin;
}

QScrollBar::sub-line:horizontal {
	border: 1px solid black;
	background: purple;
	width: 16px;
	subcontrol-position: left;
	subcontrol-origin: margin;
}

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