Mixamo -> Blender -> Unity hierarchy messed up

Hello there, guys has anyone came across such issue or maybe have any idea how to solve it: there's an Mixamo animation which works perfectly fine in Unity.

I imported it to blender though to do some fixes to the motion.

After exporting it I am unable to use previosly defined avatar because Blender adds "Armature" object on top of the mixamo hierarchy and Unity throws import error message that it's unable to find "Armature" transform in HumanDefinition.

So before blender round trip it looked like this:

mixamo:hips
+ mixamo:spine1
+ + etc.

I made an avatar from this which I reuse for all other animations.
After blender export it looks like this:

Armature
+ mixamo:hips
+ + mixamo:spine1

How to fix it?

Thanks,
S.