diff --git a/services/web/frontend/js/ide/pdf/controllers/PdfJsMetrics.js b/services/web/frontend/js/ide/pdf/controllers/PdfJsMetrics.js
index b3c3d3b203..469db5ebe0 100644
--- a/services/web/frontend/js/ide/pdf/controllers/PdfJsMetrics.js
+++ b/services/web/frontend/js/ide/pdf/controllers/PdfJsMetrics.js
@@ -1,7 +1,13 @@
 import { v4 as uuid } from 'uuid'
 import { sendMB } from '../../../infrastructure/event-tracking'
 
+// VERSION should get incremented when making changes to caching behavior or
+//  adjusting metrics collection.
+// Keep in sync with the service worker.
+const VERSION = 2
+
 const pdfJsMetrics = {
+  version: VERSION,
   id: uuid(),
   epoch: Date.now(),
   totalBandwidth: 0,
diff --git a/services/web/frontend/js/serviceWorker.js b/services/web/frontend/js/serviceWorker.js
index ac048ed0bd..57fa7c88d0 100644
--- a/services/web/frontend/js/serviceWorker.js
+++ b/services/web/frontend/js/serviceWorker.js
@@ -3,6 +3,7 @@ const OError = require('@overleaf/o-error')
 
 // VERSION should get incremented when making changes to caching behavior or
 //  adjusting metrics collection.
+// Keep in sync with PdfJsMetrics.
 const VERSION = 2
 
 const CLEAR_CACHE_REQUEST_MATCHER = /^\/project\/[0-9a-f]{24}\/output$/