The Enlarged Board of Appeal of the European Patent Office has been asked whether the introduction of a disclaimer into a patent claim can constitute an undue broadening of that claim. Now, the Enlarged Board of Appeal has rendered some guidelines: The introduction of the disclaimer constitutes an undue broadening if the subject matter – after introduction – remaining in the claim is not directly and unambiguously, be it explicitly or implicitly disclosed to the skilled person. Whether this is the case or not requires a technical assessment of the overall technical circumstances of the case and the relationship between the subject matter remaining in the claim after the amendment with regard to the disclosure of the application as filed.