diff --git a/src/slic3r/GUI/GUI_ObjectList.cpp b/src/slic3r/GUI/GUI_ObjectList.cpp
index d83187a81..79b8eae52 100644
--- a/src/slic3r/GUI/GUI_ObjectList.cpp
+++ b/src/slic3r/GUI/GUI_ObjectList.cpp
@@ -2179,9 +2179,9 @@ void ObjectList::load_mesh_part(const TriangleMesh &mesh, const wxString &name,
     // apply the instance transform to all volumes and reset instance transform except the offset
     apply_object_instance_transfrom_to_all_volumes(mo);
 
+    double old_top_position = mo->mesh().bounding_box().max(2) - mo->instances[0]->get_offset().z();
     ModelVolume* mv = mo->add_volume(mesh);
-    Vec3d instance_bbox = mo->mesh().bounding_box().size();
-    Vec3d offset = Vec3d(0, 0, instance_bbox[2] / 2 + mv->get_offset(Axis::Z));
+    Vec3d offset = Vec3d(0, 0, old_top_position + mv->get_offset(Axis::Z));
     mv->set_offset(offset);
     mv->name = name.ToStdString();
     if (!text_info.m_text.empty())