diff --git a/src/manifold/src/csg_tree.cpp b/src/manifold/src/csg_tree.cpp
index 610d3e1e1..c48d692ad 100644
--- a/src/manifold/src/csg_tree.cpp
+++ b/src/manifold/src/csg_tree.cpp
@@ -223,11 +223,12 @@ Manifold::Impl CsgLeafNode::Compose(
 
   // if we are already parallelizing for each node, do not perform multithreaded
   // copying as it will slightly hurt performance
-  if (nodes.size() > 1 && policy == ExecutionPolicy::Par)
+  if ((nodes.size() > 1 && policy == ExecutionPolicy::Par) ||
+      ManifoldParams().deterministic)
     policy = ExecutionPolicy::Seq;
 
   for_each_n(
-      nodes.size() > 1 ? ExecutionPolicy::Par : ExecutionPolicy::Seq,
+      !ManifoldParams().deterministic && nodes.size() > 1 ? ExecutionPolicy::Par : ExecutionPolicy::Seq,
       countAt(0), nodes.size(),
       [&nodes, &vertIndices, &edgeIndices, &triIndices, &propVertIndices,
        numPropOut, &combined, policy](int i) {