diff --git a/web/app.js b/web/app.js
index 6e916866..51d50f66 100644
--- a/web/app.js
+++ b/web/app.js
@@ -1803,6 +1803,9 @@ function webViewerUpdateViewarea(e) {
 }
 
 window.addEventListener('resize', function webViewerResize(evt) {
+  if (!PDFViewerApplication.eventBus) {
+    return;
+  }
   PDFViewerApplication.eventBus.dispatch('resize');
 });