Can't bake ambient occlusion

Hi, I already baked ambient occlusion to a texture but I can’t get it to work on a model I’m building.
I attached the file with a simple model to see the problem: test2.blend (487 KB)
I succeded in rendering textures but when I render ambient occlusion there’s only white faces.

Thanks in advance.

Turn of the ‘Selected to Active’ option

Ok, cool, this option is not very clear to me, I just knew I had to check it to bake textures.
Thanks for your help !

‘Selected to Active’ does what it says, it transfers some data from the selected objects to the currently active object. You are not doing this when baking the AO

OK, but is there something usefull to do by checking “Selected to Active” with “Ambient occlusion” selected and baking or doing the inverse with “Texture” ?