diff --git a/src/brep/assembly_constraints.cpp b/src/brep/assembly_constraints.cpp
index 7296654..98866ff 100644
--- a/src/brep/assembly_constraints.cpp
+++ b/src/brep/assembly_constraints.cpp
@@ -14,7 +14,7 @@ core::AABB3D node_world_bounds(const AssemblyNode* node) {
     // For root's direct children, this IS the world transform.
     const auto& T = node->local_transform;
 
-    if (node->model.has_value()) {
+    if (node->model->has_value()) {
         core::AABB3D local_bb = node->model->bounds();
         core::Point3D corners[8] = {
             local_bb.min(),