Wis. Stat. § 893.14: Limitation on use of a right of action as a defense or counterclaim.

Unless otherwise specifically prescribed by law, the period within which a cause of action may be used as a defense or counterclaim is computed from the time of the accrual of the cause of action until the time that the plaintiff commences the action in which the defense or counterclaim is made. A law limiting the time for commencement of an action is tolled by the assertion of the defense or the commencement of the counterclaim until final disposition of the defense or counterclaim. If a period of limitation is tolled under this section and the time remaining after final disposition in which an action may be commenced is less than 30 days, the period within which the action may be commenced is extended to 30 days from the date of final disposition.