diff --git a/www/common/cryptpad-common.js b/www/common/cryptpad-common.js
index 84e7d1a01..0c62084db 100644
--- a/www/common/cryptpad-common.js
+++ b/www/common/cryptpad-common.js
@@ -1373,9 +1373,11 @@ define([
 
                     console.log('Posting CONNECT');
                     postMessage('CONNECT', cfg, function (data) {
-                        // XXX validate that data exists, probably return otherwise.
+                        // XXX data should always exist
+                        // this indicates a false condition in sharedWorker
                         // got here via a reference error:
                         // uncaught exception: TypeError: data is undefined
+                        if (!data) { throw new Error('FALSE_INIT'); }
                         if (data.error) { throw new Error(data.error); }
                         if (data.state === 'ALREADY_INIT') {
                             data = data.returned;