[xmonad] Gimp -- Newer Windows Plunging Under Older Windows

Hi, I stumbled across the following 'amusing' behavior while using Gimp: quite often, newer (floating) windows go under older windows. To make those hidden windows visible, one has to move the big foreground window whose hiding them and select them with the mouse to pull them to the foreground. How can I configure xmonad so that the floating window who has focus is at the top of the window layers? Greetings, -- Bastien