diff --git a/frontend/src/pages/SessionDetailPage.tsx b/frontend/src/pages/SessionDetailPage.tsx
index 54932112..635967c8 100644
--- a/frontend/src/pages/SessionDetailPage.tsx
+++ b/frontend/src/pages/SessionDetailPage.tsx
@@ -259,7 +259,7 @@ export function SessionDetailPage() {
       const tree = await treesApi.create({
         name: flowData.name,
         description: flowData.description,
-        tree_type: flowData.tree_type,
+        tree_type: flowData.tree_type as import('@/types').TreeType,
         tree_structure: flowData.tree_structure,
         tags: flowData.tags,
       })