diff --git a/platform/firefox/bootstrap.js b/platform/firefox/bootstrap.js
index fec58275d..96c1681d9 100644
--- a/platform/firefox/bootstrap.js
+++ b/platform/firefox/bootstrap.js
@@ -60,6 +60,12 @@ function startup(data, reason) {
         }
 
         let hiddenDoc = appShell.hiddenDOMWindow.document;
+
+        if ( hiddenDoc.readyState === 'loading' ) {
+            hiddenDoc.addEventListener('DOMContentLoaded', onReady);
+            return;
+        }
+
         bgProcess = hiddenDoc.documentElement.appendChild(
             hiddenDoc.createElementNS('http://www.w3.org/1999/xhtml', 'iframe')
         );
diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index 982a0c54f..ede2a97ff 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -65,7 +65,7 @@ vAPI.app.restart = function() {
 var cleanupTasks = [];
 
 // This must be updated manually, every time a new task is added/removed
-var expectedNumberOfCleanups = 7;
+var expectedNumberOfCleanups = 6; // 7 instances of cleanupTasks.push, but one is unique to fennec, and one to desktop.
 
 window.addEventListener('unload', function() {
     for ( var cleanup of cleanupTasks ) {