Wis. Stat. § 409.507
Sub. (3) is amended eff. 7-1-13 by 2011 Wis. Act 206 to read:
(3) Change in debtor's name. If the name that a filed financing statement provides for a debtor becomes insufficient as the name of the debtor under s. 409.503(1) so that the financing statement becomes seriously misleading under s. 409.506:
(a) The financing statement is effective to perfect a security interest in collateral acquired by the debtor before, or within 4 months after, the filed financing statement becomes seriously misleading; and
(b) The financing statement is not effective to perfect a security interest in collateral acquired by the debtor more than 4 months after the filed financing statement becomes seriously misleading, unless an amendment to the financing statement which renders the financing statement not seriously misleading is filed within 4 months after the financing statement became seriously misleading.