diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 2be376d50378..4ac86901929b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -92,6 +92,9 @@ jobs:
       - name: build web app
         run: |
           node webapp --disable-minify
+      - name: build calendar web app
+        run: |
+          node webapp --disable-minify --app calendar
       - name: check for FIXMEs
         run: |
           if grep "FIXME\|[fF]ixme" -r src buildSrc test/tests packages/*/lib app-android/app/src app-ios/tutanota/Sources; then
diff --git a/buildSrc/buildWebapp.js b/buildSrc/buildWebapp.js
index 25a0a0e1d1ca..e7bb0856222b 100644
--- a/buildSrc/buildWebapp.js
+++ b/buildSrc/buildWebapp.js
@@ -34,6 +34,7 @@ export async function buildWebapp({ version, stage, host, measure, minify, proje
 	const buildDir = isCalendarApp ? "build-calendar-app" : "build"
 	const entryFile = isCalendarApp ? "src/calendar-app/calendar-app.ts" : "src/mail-app/app.ts"
 	const workerFile = isCalendarApp ? "src/calendar-app/workerUtils/worker/calendar-worker.ts" : "src/mail-app/workerUtils/worker/mail-worker.ts"
+	const builtWorkerFile = isCalendarApp ? "calendar-worker.js" : "mail-worker.js"
 
 	console.log("Building app", app)
 
@@ -146,7 +147,7 @@ export async function buildWebapp({ version, stage, host, measure, minify, proje
 	await fs.promises.writeFile(
 		`${buildDir}/worker-bootstrap.js`,
 		`importScripts("./polyfill.js")
-const importPromise = System.import("./worker.js")
+const importPromise = System.import("./${builtWorkerFile}")
 self.onmessage = function (msg) {
 	importPromise.then(function () {
 		self.onmessage(msg)