The lyrics actually go "Well there's gonna be a time, When I'm gonna change your mind" by the way. In the Past Masters version, Paul can be heard singing the right lyrics, while John sings "make you mine" instead of "change your mind". It is change your mind, because in the Anthology 1 version where they sing it live, they both sing "change your mind." But, both work in the song really. John was pretty infamous for not singing the right lyrics... he did a similar thing in "Slow Down" and again in "Hey Jude"
The lyrics actually go "Well there's gonna be a time, When I'm gonna change your mind" by the way. In the Past Masters version, Paul can be heard singing the right lyrics, while John sings "make you mine" instead of "change your mind". It is change your mind, because in the Anthology 1 version where they sing it live, they both sing "change your mind." But, both work in the song really. John was pretty infamous for not singing the right lyrics... he did a similar thing in "Slow Down" and again in "Hey Jude"