Parenting cause object to morph

takanuinuva_40f6ab6ae5

I'm trying to parent a genesis 2 model to a morphing python bone to create a Lamia but each time I try the genesis 2 model's bones and scale changes. I've tried parenting in place but it still keeps moving.

How can I lock the genesis 2 model's bones so they don't morph when parenting.