Optimizing (CSS) breaks wordpress admin bar

Hi,

I really like this plugin and the Async javascript ‘companion’ plugin. When I turn on the CSS optimization in the settings, the wordpress admin bar breaks. Normally it’s folded into a small black bar at the top of the screen. However, if you turn the CSS optimization on and then view the website, the content of the admin bar spills out in a list and isn’t hidden, creating a long and unclear list.

I’ve tried turning off various things (as I first suspected it was an issue with Async Javascript) but nothing solves the problem other than turning off optimizing the CSS.

Has anyone else had this experience? How can I solve this?