Avatars open their mouth when mirroring animation

When setting up an avatar’s animation (Mecanim), clicking on the “mirror” option results in the animation mirroring satisfactorily except the mouth which gets opened. I have been getting this problem with the “Dude” character with its stock animation and with other characters with other animations.

I’m using Unity 4.0.0f3.

Have any of you got this same issue?, any idea on how to solve it?.

Thanks.

Yes, I have exactly the same issue. Seems that mirroring is the expected way to produce reversed animations (eg a right turn from the available left) but this prevents that approach. Anyone got a solution?