Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
You can force it to just hibernate instead of safe sleep, though, if you are trying to save battery.
 
How do I do this?

Type this into the terminal and hit enter:

sudo pmset -a hibernatemode 1



EDIT NOTE: This affects all instances of sleep, not just closing the lid. I don't think there is any way to specify a setting just for that. If you want to undo it, repeat the command, but give "hibernatemode" the value of "3". Also, a value of "0" makes it suspend directly to RAM and fall asleep instantly, without bothering to write the safe sleep file.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.