Rule 15(c)(1)(B) provides that an amendment relates back to the date of the original pleading when 'the amendment asserts a claim or defense that arose out of the conduct, transaction, or occurrence set out-or attempted to be set out-in the original pleading.' 'The criterion of relation back is whether the original complaint gave the defendant enough notice of the nature and scope of the plaintiff's claim that he shouldn't have been surprised by the amplification of the allegations of the original complaint in the amended one.' Santamarina v. Sears, Roebuck & Co., 466 F.3d 570, 573 (7th Cir. 2006).