diff --git a/support.js b/support.js
index bf90a390..9aaa0145 100644
--- a/support.js
+++ b/support.js
@@ -67,7 +67,7 @@ const registerHooks = () => {
 
     const saveCoverageObject = (win) => {
       // if application code has been instrumented, the app iframe "window" has an object
-      const applicationSourceCoverage = win.__coverage__
+      const applicationSourceCoverage = win?.__coverage__
       if (!applicationSourceCoverage) {
         return
       }