u/Wakinta

In 574 from Hesiod's Work and Days it says:

φεύγειν δὲ σκιεροὺς θώκους καὶ ἐπ᾽ ἠόα κοῖτον

translation: Avoid shady seats and sleeping until dawn

is ἠόα an irregular accusative of ΗΩΣ ?

the accusative I found is ἠῶ or ἠοῦν, what is happening here?