In this study, I enquire into word-formation semantics and the way context specifies the reading of derived words. In particular, I use the apparatus of Frame Semantics and offer a treatment of lexical stereotype negation that is expressed in English by the prefixes non- (e.g. nonanswer, noncolor) and un- (e.g. unpolitician, un-diva). In order to account for this phenomenon, I introduce a formal treatment of lexical rules in Frame Semantics, making use of the formalism of attribute-value matrices. I also use corpus-extracted data to enquire into the way context impacts on scope properties. I motivate an analysis under which the “absence” of a characteristic of the base lexeme is treated as a change in the value of an attribute of the base lexeme. The treatment of lexical stereotype negation can advance our understanding of modification in word-formation semantics and lead to a more balanced analysis and understanding of all major categories.