diff --git a/src/user/user_objects.cc b/src/user/user_objects.cc
index dd21fab0..997bcde4 100644
--- a/src/user/user_objects.cc
+++ b/src/user/user_objects.cc
@@ -301,7 +301,6 @@ void mjCBoundingVolumeHierarchy::CreateBVH() {
     if (bvleaf_[i].conaffinity || bvleaf_[i].contype) {
       BVElement element;
       element.e = &bvleaf_[i];
-      element.index = i;
       mjtNum vert[3] = {element.e->pos[0] - ipos_[0],
                         element.e->pos[1] - ipos_[1],
                         element.e->pos[2] - ipos_[2]};
@@ -398,10 +397,10 @@ int mjCBoundingVolumeHierarchy::MakeBVH(
   axis = edges[axis] > edges[2] ? axis : 2;
 
   // find median along the axis
-  auto m = nelements/2;
-  // Note: nth element performs a partial sort of elements
+  // note: nth_element performs a partial sort of elements
   BVElementCompare compare;
   compare.axis = axis;
+  int m = nelements / 2;
   std::nth_element(elements_begin, elements_begin + m, elements_end, compare);
 
   // recursive calls
diff --git a/src/user/user_objects.h b/src/user/user_objects.h
index a62436e1..01333478 100644
--- a/src/user/user_objects.h
+++ b/src/user/user_objects.h
@@ -146,8 +146,6 @@ class mjCBoundingVolumeHierarchy : public mjCBoundingVolumeHierarchy_ {
   // internal class used during BVH construction, for partial sorting of bounding volumes
   struct BVElement {
     const mjCBoundingVolume* e;
-    // index of the element in the original input to BVH, used to ensure a stable sort
-    int index;
     // position of the element in the BVH axes
     mjtNum lpos[3];
   };
@@ -159,7 +157,8 @@ class mjCBoundingVolumeHierarchy : public mjCBoundingVolumeHierarchy_ {
       if (e1.lpos[axis] != e2.lpos[axis]) {
         return e1.lpos[axis] < e2.lpos[axis];
       }
-      return e1.index < e2.index;
+      // comparing pointers gives a stable sort, because they both come from the same array
+      return e1.e < e2.e;
     }
   };