diff --git a/app/index.js b/app/index.js
index 4f59d24de..08055689b 100644
--- a/app/index.js
+++ b/app/index.js
@@ -37,7 +37,7 @@ if ("serviceWorker" in window.navigator) {
       }
     );
 
-    if (maybePromise) {
+    if (maybePromise && maybePromise.then) {
       maybePromise
         .then((registration) => {
           console.log("SW registered: ", registration);