Slider app focus related bug

Just discovered a bug with the slider / mousewheel operation.

You can see it in the Juce Demo. If the app doesn’t have focus (put it next to another window and select that one), it will still respond to mouse-wheel activity when hovering over the slider control, but it will only increase, even when scrolling downwards! When you select the app again, the behaviour is normal.

When I tried this the app didn’t receive any wheel messages unless it was active… I wonder if it’s something specific to the mouse-driver?