Second and subsequent QTextEdit.setPalette() calls are ignored

When I start up my PySide application I call this method:

def changeBackground(self, bg):
palette = self.lineEdit.palette()
palette.setBrush(QPalette.Base, QBrush(bg))
self.lineEdit.setPalette(palette)
palette = self.textEdit.palette()
palette.setBrush(QPalette.Base, QBrush(bg))
palette.setBrush(QPalette.Window, QBrush(bg))
self.textEdit.setPalette(palette)

bg is a QColor or a QPixmap; self.lineEdit is a QLineEdit and self.textEdit is a QTextEdit.

This works the first time I call it.

But the second and subsequent times I call it, it works correctly for the QLineEdit; but has no effect on the QTextEdit. I have tried setting autofillbackground on and off and it has no effect.