Root bone changed

Hi, all.

I’m exported 3d model of my character from Unity to Blender and changed rig.
After importing backwards to Unity, my mesh changed root bone in skinned mesh renderer.

How unity get information about root bone in skinned mesh renderer and how can i change it?

Before:

.

After:

Found the reason. Blender destroy hierarchy when import fbx.

Sorry for digging up an old post but do you remember what you did to fix this? Did you change your export settings?