diff --git a/src/brep/assembly_constraints.cpp b/src/brep/assembly_constraints.cpp
index ee55b44..19aff9a 100644
--- a/src/brep/assembly_constraints.cpp
+++ b/src/brep/assembly_constraints.cpp
@@ -15,7 +15,7 @@ core::AABB3D node_world_bounds(const AssemblyNode* node) {
     const auto& T = node->local_transform;
 
     if (node->model.has_value()) {
-        core::AABB3D local_bb = node->model.bounds();
+        core::AABB3D local_bb = node->model.value().bounds();
         core::Point3D corners[8] = {
             local_bb.min(),
             core::Point3D(local_bb.max().x(), local_bb.min().y(), local_bb.min().z()),