XF 1.4 Adding Shadow to Tabs

That's not quite the phrasing I mean to use in the title, but I'm having a slight issue adding shadow to the side of the content section, specifically the bit underneath a selected tab. As you can see in the attached image, the shadow looks perfectly fine everywhere except in this one place. So essentially my question is: which style property controls this specific portion? Any help would be greatly appreciated!

Last edited: