diff --git a/imports/startup/server/calcUnionAsync.js b/imports/startup/server/calcUnionAsync.js
index 6e00c03..0eaa57f 100644
--- a/imports/startup/server/calcUnionAsync.js
+++ b/imports/startup/server/calcUnionAsync.js
@@ -1,6 +1,16 @@
 import path from 'path';
 import { Worker } from 'worker_threads';
 
+// Meteor only bundles the npm packages it sees imported/required somewhere in
+// its own compiled module graph. The actual usage of these three is inside
+// private/workers/unionWorker.js, a plain asset file Meteor's bundler never
+// traces (it's loaded at runtime via new Worker(), not import/require here).
+// Without this, `meteor build` drops them from programs/server/node_modules
+// and the worker fails at startup with "Cannot find module '@turf/circle'".
+import '@turf/circle';
+import '@turf/union';
+import '@turf/truncate';
+
 const WORKER_PATH = path.resolve(process.cwd(), 'assets/app/workers/unionWorker.js');
 
 /**