Very good. Actually, I'm inclined just to change it. It's very rarely if ever used in user programs. And even it is - it will fail to compile and be an easy fix for anyone who upgrades. Robert Ramey Dan Bikel wrote:

The struct boost::serialization::tracking_level has a misspelled constant. Instead of it having a constant named "track_selectively", the constant is misspelled "track_selectivly". For backward compatibility, I would add a new constant with the correct spelling that has the value of the old, misspelled constant.

(This bug exists in v. 1.33.1 of boost.)

--Dan.