Distinguishing backfaces from frontfaces in Bullet Ray Test

I want to determine whether the hits I get by performing a BulletWorld.rayTestAll() are hitting the faces of a mesh from the front or the back.

However, the normals that I get are always flipped so that they face the same way, even when I clearly hit a backface.

The meshes are added via BulletRigidBodyNode.add_shapes_from_collision_solids().

I thought I could use the triangle_index, but the hit node contains multiple shapes but getShapePart always returns 0. (Is this a bug? getShapePart doesn’t have a clear description in the documentation…)

Is there a way to determine the direction from which a face was hit using Panda’s bullet interface?