This paper looks at the morphophonology of Hiaki (ISO639-3 yaq, Tara-Cahitic, Uto-Aztecan). Specifically, it looks at "echo vowels": apparent sequences of identical vowels separated by a glottal stop (henceforth V1'V1) which appear in some lexically and morphologically conditioned contexts. These sequences do not appear to be constrained to certain parts of the word: they can be found word-finally (vo'o 'road'), morpheme-finally (kecha'a-vae 'stand-PROSP'), and morpheme-internally (chi'imu 'stye'). Previous studies (e.g., Dedrick and Casad 1999) attributed their appearance to epenthetic vowel insertion, but the authors here propose that the glottal stop seen in 'echo' V1'V1 sequences is a glottal feature that is attached to certain vowels. Depending on its phonological environment, this feature surfaces as either a glottal onset (before a vowel) or a preglottalized vowel (before a consonant-initial syllable). To support these claims, we (a) present syllable-count data indicating that syllables that would be predicted to be disyllabic under an epenthesis analysis are in fact monosyllabic, (b) consider how consonant-initial morphemes can trigger echo vowels where they are not seen with vowel-initial allomorphs (ex: -u / -wi), and (c) compare Hiaki and Mayo cognates in which the Mayo word has an echo vowel and following consonant (/l/ or /r/) that the Hiaki word lacks.