Using additional layer options with Infolayer

I am using olwidget with django and have created a map with multiple infolayers. It works well but I would like to have some of the infolayers switched off by default, when the page loads. I have been trying to add 'visibility': False to the layer options for the layers I want switched off, but it doesn't seem to work. Does anyone know why this might not work?

Cheers
Tom
