Lexical innovations (e.g., zero-derivations coined on the fly by a speaker) seem to bear semantic content. Yet, such expressions cannot bear semantic content as a function of the conventions of meaning in force in the language, since they are not part of its lexicon. This is in tension with the commonplace view that the semantic content of lexical expressions is constituted by linguistic conventions. The conventionalist has two immediate ways out of the tension. The first is to preserve the conventionalist assumption and deny that lexical innovations bear semantic content. The second is to dynamicize the conventionalist assumption, that is, argue that presentations of unattested expressions trigger an augmentation of the standing semantic resources of the language and instantiate content as a result of this underlying update. Building on a comparison with the production of novel onomatopoeic words, iconic pseudowords and pro-speech gestures, the paper argues that the issue is best addressed by suspending the conventionalist assumption, and describes the metasemantic implications of the claim.