Originally, Ancient Greek employed the letter digamma ( ϝ) to represent the /w/ sound. Over time, this sound disappeared, alongside the digamma that denoted it. However, to transcribe those archaic, dialectal, or foreign words that still retained this sound, lexicographers employed other letters, whose sound was close enough to /w/. Among these, there is the letter gamma (γ), attested mostly but not only in the Lexicon of Hesychius. Given what we know about the sound of gamma, it is difficult to explain this use. The most straightforward hypothesis suggests that the scribes who copied these words misread the capital digamma (Ϝ) as gamma (Γ). Presenting new and old evidence of gamma used to denote digamma in Ancient Greek literary and documentary papyri, lexicography, and medieval manuscripts, this paper refutes this hypothesis, and demonstrates that a peculiar evolution in the pronunciation of gamma in Post-Classical Greek triggered a systematic use of this letter to denote the sound once represented by the digamma.