QGLWidget in QScrollArea says "invalid drawable"

When I display my QGLWidget in the layout of my main QWidget, everything is fine. When I put the QGLWidget into a QScrollArea, and then 开发者_运维问答display, Python says:

2011-05-14 19:10:28.900 Python[68311:613] invalid drawable

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Making the widget resizable seemed to fix the problem.