diff --git a/services/web/app/src/Features/Project/ProjectHelper.js b/services/web/app/src/Features/Project/ProjectHelper.js
index e7c0232b6b..adbe006328 100644
--- a/services/web/app/src/Features/Project/ProjectHelper.js
+++ b/services/web/app/src/Features/Project/ProjectHelper.js
@@ -1,3 +1,4 @@
+// ts-check
 const { ObjectId } = require('mongodb')
 const _ = require('lodash')
 const { promisify } = require('util')
diff --git a/services/web/app/src/Features/Project/ProjectListController.js b/services/web/app/src/Features/Project/ProjectListController.js
index 64d39511e9..3e107fb49d 100644
--- a/services/web/app/src/Features/Project/ProjectListController.js
+++ b/services/web/app/src/Features/Project/ProjectListController.js
@@ -1,3 +1,4 @@
+// ts-check
 const _ = require('lodash')
 const Metrics = require('@overleaf/metrics')
 const Settings = require('@overleaf/settings')
diff --git a/services/web/app/src/Features/Subscription/SubscriptionViewModelBuilder.js b/services/web/app/src/Features/Subscription/SubscriptionViewModelBuilder.js
index 0f72b0809b..4bcb1e9988 100644
--- a/services/web/app/src/Features/Subscription/SubscriptionViewModelBuilder.js
+++ b/services/web/app/src/Features/Subscription/SubscriptionViewModelBuilder.js
@@ -1,3 +1,4 @@
+// ts-check
 const Settings = require('@overleaf/settings')
 const RecurlyWrapper = require('./RecurlyWrapper')
 const PlansLocator = require('./PlansLocator')
diff --git a/services/web/app/src/Features/Survey/SurveyHandler.js b/services/web/app/src/Features/Survey/SurveyHandler.js
index 1e03e71e3b..27e0c663a6 100644
--- a/services/web/app/src/Features/Survey/SurveyHandler.js
+++ b/services/web/app/src/Features/Survey/SurveyHandler.js
@@ -1,3 +1,4 @@
+// ts-check
 const crypto = require('crypto')
 const SurveyCache = require('./SurveyCache')
 const SubscriptionLocator = require('../Subscription/SubscriptionLocator')