A limitation on the application of the doctrine of equivalents under German patent law. The Formstein defence precludes the extension of claims under the German version of the doctrine to encompass (or cover) embodiments that are not novel (i.e., found in the prior art) or are obvious in light of the prior art. In effect, the German doctrine of equivalents cannot apply if the accused product or method itself would not be considered a patentable invention over the relevant prior art. This defence is referred to in German as Formstein-Einwand.