ABSTRACT The paper deals with the fourth palatalization of velars in the Kryvorivnja dialect, one of the southeastern Hutsul dialects of Southwest Ukrainian, in its connection with the tendency toward intrasyllabic harmony constraint introduced in Common Slavic. A new interpretation of the concept of intrasyllabic harmony is offered with respect to the tonality feature of flatness (rounding) for Common Slavic and Southwest Ukrainian: most of the Kryvorivnja consonants are palatalized after unrounded vowels and non-palatalized after rounded vowels. Based on the calculation of sound formants in the Praat program, I argue that the fourth palatalization serves as a requirement for the change of Common Slavic *o in the Kryvorivnja dialect. This is why the dialect largely renders Common Slavic *o as rounded vowel formants after nonsharped consonants and unrounded vowel formants after sharped consonants.