Tuplets with multiple voices

I'm trying to transcribe a piece on piano, and to make it easily readable I need to have quarter notes in voice one and some triplets in voice two, but this is impossible. I'm not sure why it works this way, but apparently you can only use triplets in a secondary voice if triplets are used in the first voice. This is very frustrating, and if it could be changed I would be very happy.
Update: I realised this song is supposed to be in 12/8 rather than 4/4, so this isn't still a problem for me, though I still think it should be changed.