Extra padding in QComboBox drop down on Linux and MacOS

Hello,

When adding a style sheet to a comboBox, there seems to be some extra padding added to the the dropdown. As far as I can tell this only effects Linux and MacOS as I do not see this issue when running on Windows. 

I have attached an example, which should show the problem, as well as two images of the same code, one running on Windows and the other on Linux. This does not seem to be an issue with the way the styleSheet is applied as the issue does not show on on Windows

Please see attached.