Mississippi Circuit Court Rule 7.09:

All indictments may be amended as to form but not as to the substance of the offense charged. Indictments may also be amended to charge the defendant as an habitual offender or to elevate the level of the offense where the offense is one which is subject to enhanced punishment for subsequent offenses and the amendment is to assert prior offenses justifying such enhancement (e.g., driving under the influence, Miss. Code Ann. § 63-11-30). Amendment shall be allowed only if the defendant is afforded a fair opportunity to present a defense and is not unfairly surprised.