Well Bob may or may not be right... Your Em has certainly become G#m but more info would be needed to determine the key of the song.

I'd have thought if the chord you are focusing on is the minor chord, the song is most likely a song in a minor key and it's more likely the key is G#minor...

If root chord of what you were playing was a G shape capoed up 4, Bob's answer would be correct.

Jon