QGLWidget in QMdiSubWindow does not draw or crashes

A QGLWidget set as a QMdiSubWindow does not perform any drawing (though it does clear the proper background color and paintGL is called). In some cases, it crashes with (ASSERT: "backingStore" in file kernel\qwidgetbackingstore.cpp, line 88)

This also happens with a MDI QGraphicsView with a QGLWidget viewport. This did not happen under Qt 4.x and does not happen if the GL widget is not a child of QMdiArea.