This paper provides new evidence in support of the hypothesis that the syntax–prosody mapping of Intonational Phrases is flexible (Hamlaoui and Szendrői 2015). In the traditional ‘rigid’ approaches, Intonational Phrases are taken to map onto particular syntactic projections. In contrast, in the ‘flexible’ approach, the Intonational Phrase corresponds to the highest projection of the verb (HVP). Accordingly, the ‘flexible’ approach predicts that the HVP should also determine the size of Intonational Phrases in a language where the verb height depends on the utterance type. Our evidence comes from a language of this type, Iron Ossetic (East Iranian). First, we demonstrate that verbs in Iron Ossetic occupy different functional heads in different contexts. Then, based on novel prosodic data, we show that the HVP indeed directly determines the size of Intonational Phrases in clauses with narrow foci and negative indefinites. Additionally, in wh-questions, language-specific mapping constraints come into play.