QPainter::drawText in a QGLWidget leaves a shader program in effect

Starting with Qt 4.6, creating a QPainter in a QGLWidget's paintEvent method and calling QPainter::drawText calls glUseProgramObject_ARB, but does not unset the program before returning, causing all subsequent OpenGL drawing commands to fail spectacularly. Trying to work round this by calling glUseProgram(0) after calling drawText doesn't work because the next call to drawText won't reinstate the shader program.