Thumbnail backgrounds are black when printing with Chrome

Created by: xmf

I'm experiencing a print problem in Chrome that has previously been reported here:

http://stackoverflow.com/questions/12955718/twitter-bootstrap-how-to-print-thumbnails-as-same-as-screen

Even when using a print.css to make them white, my thumbnails backgrounds stay black in Chrome. Safari, Firefox and IE look fine. Is this a Bootstrap or browser issue?