diff --git a/platform/firefox/bootstrap.js b/platform/firefox/bootstrap.js
index 95c2f1532..e48c9c733 100644
--- a/platform/firefox/bootstrap.js
+++ b/platform/firefox/bootstrap.js
@@ -60,6 +60,19 @@ function startup(data, reason) {
         }
 
         let hiddenDoc = appShell.hiddenDOMWindow.document;
+
+        // https://github.com/gorhill/uBlock/issues/10
+        // Fixed by github.com/AlexVallat:
+        //   https://github.com/chrisaljoudi/uBlock/issues/1149
+        //   https://github.com/AlexVallat/uBlock/commit/e762a29d308caa46578cdc34a9be92c4ad5ecdd0
+        if ( hiddenDoc.readyState === 'loading' ) {
+            hiddenDoc.addEventListener('DOMContentLoaded', onReady);
+            return;
+        }
+
+        // I believe this needs to be called in case it was added above.
+        hiddenDoc.removeEventListener('DOMContentLoaded', onReady);
+
         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 fe8c6e446..b01012cc3 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -65,7 +65,11 @@ vAPI.app.restart = function() {
 var cleanupTasks = [];
 
 // This must be updated manually, every time a new task is added/removed
-var expectedNumberOfCleanups = 7;
+
+// Fixed by github.com/AlexVallat:
+//   https://github.com/AlexVallat/uBlock/commit/7b781248f00cbe3d61b1cc367c440db80fa06049
+//   7 instances of cleanupTasks.push, but one is unique to fennec, and one to desktop.
+var expectedNumberOfCleanups = 6;
 
 window.addEventListener('unload', function() {
     for ( var cleanup of cleanupTasks ) {