Problem with joining armatures

Hello! so i am making a character rig, my problem is that when i join two armatures, you can see in the video that all the bones in the other armature rotates. how do i stop this from happening?

Here is the blend file:
character body V1 - combine.blend (2.5 MB)
also, i’m in version 2.79

Don’t use armatures with unapplied rotation or scale; don’t use them with models with unapplied rotation or scale. If you want to rotate an armature to fit a different model, do it in edit mode.