MDI flickering when switching between tabs

Our Qt application renders into an MDI tabbed interface in a Qt window. The problem is that when switching between the tabs there is a brief flicker as the MDI background is erased and then redrawn with the contents of the current tab. Although Qt provides the Qt::WA_PaintOnScreen flag, there doesn't seem to be any way to hook into whatever mechanism Qt uses to determine whether to erase the background or use some other sort of double-buffering technique. The flicker happens 50-75% of the time that we switch between tabs, and is most noticeable when 3 or more tabs are open at once.