[xmonad] Drag-and-drop and window focus

When I use the mouse to drag between applications (for example, drag a file from Thunar and drop it on GVim), the focus remains with the source window. I have to take some additional action to move the focus. While I understand the reasons for this behaviour, I'm finding it quite counter-intuitive, and I keep typing into the wrong window. Would it be feasible to change this? Thanks /J