http://support.apple.com/kb/HT4178

To be more specific:
"A Mac OS X v10.6.8 image created using the combo updater will support all Macs that support Mac OS X v10.6.x Snow Leopard. This includes support for the MacBook Pro (Early 2011) and iMac (Mid 2011) models."

Good news, thanks for posting. Time to cut a new base image.